This is basically my take on how the Psychic Power system should function.

The rules here make a few assumptions; firstly, they're designed with AP in mind, as per the original DH2e beta. This can easily be changed to fit the current action economy, though. I just have it in my writeup this way because my current houserules use AP.

As well, any reference to Perils tables refer to the original DH2e beta tables, which were much shorter than the current table (1-30 instead of 1-100), and were discipline specific. If anyone needs these to get a better understanding of the rules, I'm sure I can upload them without risking FFG's wrath too much.

Also, I've intentionally omitted XP costs because I'd rather get a functioning framework going before I evaluate how much XP things are worth.

Anyway, enough rambling, onto the rules!

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Psy Rating and Discipline Rating

There are two values by which a Psyker’s ability is measured. These both play a part in the manifestation of Psychic Powers.

Psy Rating is the measure of a Psyker’s raw natural power as a Psyker. This is rated on a scale of 0-3, with zero being no psychic potential, and 3 being the maximum a Player Character may ever achieve. Psy Rating also measures the number of Disciplines a Psyker has access to. Psy Rating is raised using experience points.

Discipline Rating measures a Psyker’s mastery of a specific Discipline. Like Psy Rating, this is measured on a 0-3 scale. A Psyker may only purchase points in as many Disciplines as he has Psy Rating, meaning the maximum number of Disciplines a Psyker may ever access is three. Discipline Rating may be raised using experience points.

Manifesting Powers

Manifesting powers is a relatively straightforward roll. First, determine which Characteristic to roll against. Each Psychic Discipline uses a different Characteristic.

Biomancy is governed by Toughness

Divination is governed by Perception

Pyromancy is governed by Willpower

Telekinesis is governed by Intelligence

Telepathy is governed by Fellowship

Next, determine Psy Level. Psy Level is the combination of your Psy Rating and your Discipline Rating in the appropriate Discipline. These values added together make up your Psy Level. You may choose to manifest powers at a lower Psy Level than your total value, but never a higher one, and never at zero.

Finally, make a Characteristic Test based on your chosen Discipline’s Characteristic, adding a +5 modifier for each point of Psy Level. If the test is passed, the Psychic Power is manifested .

Example

Royous is attempting to manifest a Divination power. Because Divination is governed by Perception, Royous must test against his Perception Characteristic, which is 40. Royous must then decide what Psy Level he wishes to cast the power at. Because he has a Psy Rating of 2 and a Divination Discipline Rating of 3, his maximum Psy Level for Divination powers is 5. Royous decides to cast at a lower level to reduce the risk of something going wrong, opting to cast his power at Psy Level 4.

Because he’s casting his power at Psy Level 4, he adds +20 to his Perception test. This means he’s rolling against a target number of 60 (40+20). Royous rolls a 50, passing the test. His power manifests without a hitch!

Perils of the Warp

Accessing the raw power of the Warp is never without risk, and can often lead to things going horribly wrong. Every time a Psychic Power is manifested, there’s a risk of Perils of the Warp.

If the Characteristic Test to manifest your power comes up with doubles on the dice (regardless of whether you succeed or fail), this means Perils of the Warp have occurred. Roll 2d10, adding 2 to the result for every point of Psy Level you’ve chosen to manifest the power at. Then refer to the Perils of the Warp table for your chosen discipline, applying the effects listed for your result.

Example

While attempting to manifest a Pyromancy power, Royous’ roll comes up as 11. Because he was rolling against a target number of 50, he passes with flying colours. However, the doubles on the dice mean Royous has triggered Perils of the Warp.

Royous rolls 2d10, the dice coming up 5 and 7 (12 all up). Because he was manifesting his power at Psy Level 3, he adds 6 to the result (3x2=6), meaning his final Perils of the Warp result is 18. Royous then compares this number to the Pyromancy Perils of the Warp table. Royous has generated the Greedy Warpfire effect, which is applied immediately in addition to any effects from the power he was manifesting.

Major Powers

Major Powers are potent manifestations of a Psyker’s will, each requiring dedicated training. Because of this, Major Powers must be purchased with experience points. Having at least one point in a discipline is required to purchase Major Powers belonging to that discipline.

Major Powers consist of two functionally separate effects; the standard Major Power effects and a pushed version. Pushed Powers are far more potent versions of standard Major Powers, but come with much greater risks.

The following special rules apply to Pushed Powers –

• The test to manifest a pushed power gains a +20 bonus. This is in addition to the modifier granted by Psy Level.
• Pushed Powers always generate a Perils of the Warp result. Additionally, this Perils roll gains a +3 modifier for each point of Psy Level, rather than the usual +2.

Major Powers each have a profile, containing the following –

• Time: The time taken to manifest the power, listed in AP. If it’s important to know how long a power takes to manifest in Narrative Time, assuming a direct conversion of 1AP equals two seconds.
• Sustained: Some powers may be sustained, their effects continuing for multiple rounds. If so, there will be some sort of cost listed in this category. This is the cost the Psyker must pay at the start of each round to keep a power going. The cost may be AP, Fatigue, damage, or some more esoteric sacrifices. Each sustained power also adds +1 to Perils of the Warp rolls.
• Effects: The effects of the power, which apply upon a successful manifestation roll.
• Pushed Effects: The effects of this power that apply when it is cast as a Pushed Power. These replace the standard effects, rather than adding to them.

Minor Powers

Minor Powers represent relatively insignificant applications of a Psyker’s power which don’t require dedicated training. Because of this, Minor Powers do not have to be bought as advances. Simply having a single point in a discipline grants access to all of its Minor Powers.

The following rules apply to Minor Powers –

• Any rolls on Perils of the Warp caused by Minor Powers do not add Psy Level to their result.
• Unless otherwise stated, Minor Powers take approximately five seconds to manifest (2AP in structured time).

A good starting point. I might try to build on this if that's ok with you.

Absolutely, if I didn't want things used I wouldn't post them. As long as you don't try to claim my ideas as 100% your own, I don't mind at all.

Alright, so I've edited the OP completely with some properly written up rules. To give the framework some context, here's a handful of Minor and Major powers I've drafted up. The Minor Powers are largely copypasted from Nimsim's own thread on the topic . Go check it out, it's great. Anyway, these aren't intended to be overly balanced, rather just to give a basic idea of how powers would work under my system.

Also, the Endurance ability here refers to Hit Points. They're just a part of how injuries work in my houserules. It's not too important to know the nuances of how my system works to understand these powers, but basically, PCs or other important NPCs will usually have 6 hit points. Injuries reduce these in increments of one, two or three depending on severity. Once they hit zero, you're down for the count. Any further damage and you're dead.

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Biomancy

Minor Powers

Perfect the Flesh – The psyker manipulates his body, optimising it for the task at hand. The psyker’s next Toughness, Strength or Agility based test gains a +10 modifier.

Reshape the Flesh – The psyker warps his own appearance. Select either Charm, Intimidate, or Subterfuge (Disguise). For the duration of the scene, the psyker gains a +10 modifier to any tests of the chosen skill. This power may not be used to directly mimic the appearance of another individual.

Taint the Flesh – The psyker warps a target, marking them with the foul stench of the warp. The target takes a -10 penalty to all social tests meant to leave a positive impression. As well, the target’s location may be tracked by the Psyker with a +20 Psyniscience test. These effects wear off within 24 hours, and this power may only effect one target at a time.

Rend the Flesh - The psyker stimulates the nerves to inflict a brief moment of excruciating pain on a target. The target must make a Willpower test or suffer -10 to his next action, and a point of fatigue for each two degrees of failure.

Mend the Flesh – The Psyker can diagnose the number and nature of a target’s wounds. The next Medicae test made by or contributed to by the Psyker gains a +20 modifier.

Seize the Flesh - The Psyker causes the target’s body to spasm. Select a limb. The target takes a -10 for one round to any test made using that body part.

Know the Flesh - The character is able to detect all living things within a 100m radius. The character knows the exact location of all living things within 25 meters. This lasts for the duration of the scene.

Major Powers

Iron Arm

By transmuting his flesh into living metal, the biomancer can wade through enemy fire unscathed and pulp skulls with his bare fists.

Time: 2 AP

Sustained: 1 AP

Effects: The psyker increases his Strength and Toughness by 5 x PL for the duration of the power. However, the weight of his hardened flesh weighs him down, reducing his Agility by 5 x PL, to a minimum of 10. The Toughness gain from manifesting this power does not come into effect when attempting to manifest Biomancy powers.

Pushed Effects: The psyker increases his Strength and Toughness by 10 x PL for the duration of the power. Additionally, he gains PL points of armour on all locations for the duration of the power. However, the weight of his hardened flesh weighs him down, reducing his Agility by 5 x PL, to a minimum of 10. The Toughness gain from manifesting this power does not come into effect when attempting to manifest Biomancy powers.

Enfeeble

As the Psyker channels his powers, tendrils of Warp energy lash over his victims, every caress sapping vitality from their bodies.

Time: 2 AP

Sustained: 1 AP

Effects: The psyker chooses a single target that he can see within 20 x PL meters who opposes this power with a Toughness test. If the target fails, his Strength and Toughness are reduced by 5 x PL for the duration of the power. A single target can only be affected by one instance of the Enfeeble power at a time.

Pushed Effects: The psyker chooses a single target that he can see within 20 x PL meters who opposes this power with a -20 Toughness test. If the target fails, his Strength and Toughness are reduced by 10 x PL for the duration of the power. In addition, the target suffers the Slowed condition. A single target can only be affected by one instance of the Enfeeble power at a time.

Endurance

Reaching into the essence of his allies, the biomancer knits together bones, heals flesh and banishes fatigue so that they carry on the fight.

Time: 2 AP

Sustained: Variable, see text. Only sustainable when Pushed.

Effects: The psyker chooses a number of targets up to the Psy Level of the power, all of whom must be within 3 x PL meters. This may include the psyker himself. These targets immediately recover one Hit Point or Fatigue point. The psyker then suffers fatigue equal to half his PL (rounded up) due to the strain of using this power.

Pushed Effects: The psyker chooses a number of targets up to the Psy Level of the power, all of whom must be within 3 x PL meters. This may include the psyker himself. These targets immediately recover a single Hit Point or Fatigue point, and gain the Regeneration (1) trait. The psyker then suffers fatigue equal to half his PL (rounded up) due to the strain of using this power. The Regeneration trait continues to apply so long as the power is sustained; the cost for sustaining this power is equal to half the PL (rounded up) in fatigue. This power costs no AP to sustain.

This system is pretty interesting. I like the spread between different characteristics the most. (Though Telepathy should DEFINITELY be Willpower, not Fellowship)

Also, I can't say I'm a fan of getting ALL those powers with hardly any exp investment. Thats just too much diversity. Since Powers aren't tied to aptitudes, you can easily price them all differently and at whatever you want. (50, 100, 150, so on)

Deciding on what Characteristics to assign to each discipline is tricky, for sure. My logic for Fellowship was that you can pretty easily see Fellowship as a stat relating to your ability to understand and influence others; something a lot of Telepathy powers do in a big way.

I can see the argument for moving it to Willpower, but then I'm faced with the issue of what to assign to Pyromancy. Strength, Agility and Fellowship would be my options, none of which fit too well.

As for granting all the minor powers, it's probably not a stance I'm going to back down on (although I might dial back their usefulness and make them more narrative in nature). The main goal of the minor powers is to provide a good, solid toolkit of minor manifestations that a player can access to give their discipline some proper flavour, without being too broken. Psykers having access to a range of different abilities right off the bat fits in line with my interpretation of the setting a lot better, which was one of the main motivations behind the idea.

But just think about the Psyker with 3 disciplines. If we assume 7 powers per disc, that'd be 21 free unique things they can do that no one else can. I'd rather a system more like the OW cantrip system, but a bit more crunch involved.

I'd say Strength on Pyromancy is less of a crime then Fellowship on Willpower.

That's true that it is a fairly hefty amount to get given for what amounts to a handful of advances. I do intend to make the first point of rating in a discipline particularly pricey XP wise, but even then, it might be a bit much.

I wonder if it'd be better to do it like this; nine minor powers in each discipline, for each point you buy, you get access to three of your choice. Means maxing a discipline out is needed to access every minor manifestation, and it gives raising a discipline more effect to it than just boosting your Psy Level.

Yeah, that'd be a good way to do it. And have each level be a decent chunk of exp.

Deciding on what Characteristics to assign to each discipline is tricky, for sure. My logic for Fellowship was that you can pretty easily see Fellowship as a stat relating to your ability to understand and influence others; something a lot of Telepathy powers do in a big way.

I can see the argument for moving it to Willpower, but then I'm faced with the issue of what to assign to Pyromancy. Strength, Agility and Fellowship would be my options, none of which fit too well.

As for granting all the minor powers, it's probably not a stance I'm going to back down on (although I might dial back their usefulness and make them more narrative in nature). The main goal of the minor powers is to provide a good, solid toolkit of minor manifestations that a player can access to give their discipline some proper flavour, without being too broken. Psykers having access to a range of different abilities right off the bat fits in line with my interpretation of the setting a lot better, which was one of the main motivations behind the idea.

We seem to be after the same thing but from different angels. You might be better off having the characteristic depend on the use you're puting the power to not it's discipline.

Something that concerns me much more, is the combat-orientation of most powers. This might be a copy-paste problem from OW, but it feels not more like a combat class now to be a psyker (esp. Divination, but also Telekinetics & Biomancy).

That's literally just because I was copying things over, and focused on the powers in the tabletop rulebook first. I totally intend to have a good variety in the complete system, those powers are really just there as examples.

I like what you're trying to do here, but I don't have a lot of hope that FFG will depart too far from the system they've presented us. Nothing we've seen in 2 updates has been a major change and I can't see them breaking the vaunted backwards-compatibility by revamping the psychic power rules. The update will be spelling corrections and math tweaks and maybe 1 or 2 psychic powers that got cut but not pasted.

Yeah, I really doubt FFG are going to make any major changes. I'm mostly posting this stuff as idea/copypaste fodder for people to use in their own houserules. Plus, a little feedback on my ideas before I unleash them on my group can't hurt.