Some fluff and house rules for Corruption for my swords and sorcery setting, Swords of Blackwater. Feel free to use this if you like it. There is a similar mechanic for Divine and Primal magic, called Strictures, but since I'm only allowing one spellcaster (our sorcerer) in the group, I'm not planning to detail Strictures any time soon. Suffice it to say that Divine magic is contingent upon adhering to the tenets of your faith, and straying too far or too often has consequences.

Sorcery and Corruption

“ Name? Name... it had a name once. Long ago, when it walked among the pink grubs. Like you. It sloughed off that name, like its pink grub-flesh. It became power. It became... perfection.” - The Necrophant of the Screaming Tower

Sorcery is the most powerful form of magic on Aerth. The secrets of sorcery are said to have been stolen from the demon gods by the ancient Entarens, who used those secrets to build a world-spanning empire than lasted for millennia. The Entaren Empire has long since fallen into ruin, and the greatest secrets of sorcery have been lost to time... but not all such knowledge has vanished. In the current era, there are those who thirst tirelessly for the ancient secrets, and search the ends of Aerth for more power. These latter-day sorcerers are among the most feared and dangerous men and women in the world.

It is worth noting the distinction between magic and sorcery: magic is the raw essence of Chaos, an unseen but pervasive energy that teems in the cosmos. Sorcery is the means by which that power may be bent to one's will.

Most sorcerers (who care to speak of such things) would say that the essence of sorcery comes down to two things: will, and precision. It takes great strength of mind to enact sorcery, but even more importantly, it takes immense focus and accuracy to control the magic you summon, and achieve the results you seek. Much like an engineer carefully designs and constructs a great physical work, so must a sorcerer exercise diligence and precision to enact magic. A careless witch or distracted apprentice can easily destroy themselves with sorcery, which is vastly less forgiving than a draughtsman's blueprint.

Even those with patience and skill are not immune to error and peril. Magic is a willful, unpredictable, and hostile force, never meant for mortal hands or minds. It seeks to be unbound and unleashed, and chafes against the prison a sorcerer crafts for it. Whenever possible, magic will lash out, especially against whomever has the temerity to attempt to command it.

Sorcerers, whether newly-chosen apprentice or ancient archmagos, are potentially subject to the wrath of the magic they command. This wrath is termed “Corruption”. It is not often fatal, but it can be debilitating, and over time, it can transform what was once a normal man or woman into an abomination that could never be mistaken for human. Some sorcerers seek to avoid the taint of Corruption; others embrace it, often to their ruin. To others, it is simply the price one must pay. They will gladly sacrifice their mortal forms, along with their sanity, in pursuit of godlike power.

Magic is powerful, but it is also transitive. No known magics last forever. Corruption, as a side effect of improperly managed magic, is likewise impermanent. However, the more of it there is, the more difficult it becomes to eliminate it (assuming one wishes to do so).

When a sorcerer in Swords of Blackwater (i.e. anyone using Arcana to cast spells) generates 3 or more uncancelled Setback on a spell check, or generates one or more Despair, they will be afflicted with a Rank of Corruption, in addition to any other misfortune. Corruption usually takes the form of a physical alteration, but can occasionally affect the mind. There are five Ranks of Corruption: after Rank 3, it is nearly impossible to rid oneself of the changes.

When Corruption is gained, a sorcerer may attempt to rid himself of it. To do so, he must not perform any magic for a number of weeks equal to his current Ranks of Corruption. At the end of that time, he may make a Resilience check. The difficulty of this check is one plus his current Ranks of Corruption. If he succeeds, he lowers his Corruption Rank by one. If he fails, there is no change, and he may try again after another period of magical abstention.

For each Rank of Corruption, a sorcerer suffers one Setback on Social skill checks (except Coercion). Any Setback caused by Corruption cannot be mitigated by talents (though the effects of Corruption can potentially be disguised or temporarily mitigated by more magic).

At each rank of Corruption, there also manifests one or more physical or mental afflictions, chosen by the GM. Generally afflictions are minor and easily concealed at the lower Ranks, while at Rank 4 or 5, the character is unmistakably Corrupted (and may no longer appear human). An afflictino can cause a penalty akin to a Critical Injury, or it may be purely cosmetic. Occasionally, the results are helpful (if grotesque), such as a long eyestalk emerging from one's shoulder, or one's fingers being replaced by clusters of dexterous tentacles.

Magical Maneuvers

“ Listen, boy: there is more to see than you have seen. Glorious things! I will show you. But in seeing, you too are revealed. You must learn to hide, before you can see!” - Tycho Langhorn, to his new apprentice

Sorcerers are powerful, but they invariably have many enemies. The most deadly enemies are nearly always other sorcerers. The threat of Investiture by a more cunning or powerful sorcerer is a constant risk. But, in addition to their spells and minions, sorcerers have a few other ways by which to avoid that dreaded fate.

Assense: As a maneuver, a sorcerer may extend his senses into the unseen world, in order to perceive the flows of magical energy at work. This allows him to perceive active spells and magical defenses, whether a creature is magical, and to locate users and sources of magic nearby. This is called “Assensing”. An Assensing sorcerer may make a Perception check (using Intellect instead of Cunning) to magically perceive his environment. Success on the check will reveal the most powerful source of magic within Short range. Extra successes on the check extend the range of the sorcerer's assensory field by one range band per success, to a maximum of Long range. Advantages on this check will allow the sorcerer to identify multiple sources of magic, or gain more information about a singular source. Failure on this roll means that the results are inconclusive, or too chaotic to accurately assess. Setback usually manifests as Strain.

It is important to note that while a sorcerer is Assensing, he himself becomes much more visible to others who may be Assensing as well. Some beings, including demons, spirits, ancient horrors, and other fell entities, are often alerted to the presence of a sorcerer by perceiving his arcane footprint (see below). It is advisable for most sorcerers to use this ability sparingly, and only while protected, or ready for threats.

When a sorcerer is Assensing, or making a magic skill check, he is also broadcasting his presence within the unseen world. A sorcerer's arcane footprint is equal to his Sorcery skill rating in range bands: a skill of 1 equals Short range, a skill of 2 equals Medium range, 3 equals Long range, 4 or 5 equals Extreme range.

Magically aware adversaries within the appropriate range band may become alerted to a sorcerer's presence, if he is Assensing, or if he is using powerful magic. Any spell of difficulty 3 or higher is enough to alert magically aware adversaries within the sorcerer's arcane footprint (though it will not give them additional information unless they are Assensing).

Ward: Just as Assense allows a sorcerer to use his power to gain keener insight into his environment, so does Ward allow him to guard himself from detection (and possible harm). As a maneuver, a sorcerer may Ward himself against detection and supernatural perception until the end of his next turn. No skill check is required for this, and it can be sustained as long as the sorcerer has maneuvers available. However, the sorcerer cannot cast spells, or Assense, while using the Ward maneuver.

If an adversary is actively attempting to locate a sorcerer who is using Ward, it becomes an opposed Perception vs. Discipline check. If the adversary wins, it becomes aware that a sorcerer is nearby. Each advantage can be used to narrow down the location of the subject; 3 Advantage, or a Triumph, allows the adversary to pinpoint the sorcerer. If the sorcerer wins the opposed check, he remains concealed. There is no benefit to additional successes, but Advantage can be used to misdirect the adversary. If the sorcerer generates Despair, his Ward falls and he is immediately revealed.

Investiture

“ Once you enter the Game, you must hunt, and thereby thrive, or become prey, and be destroyed. The Game never ends so long as you endure. The only true escape is death.” - Theobald Gant, Archmagos

Investiture is an act in which a sorcerer defeats and kills another sorcerer, and absorbs part of their power. Fear of investiture leads most sorcerers to avoid others of their kind at all costs, except as prey for their own appetites.

There are many stories and legends about investiture, and no way to be sure which of them are true. It is widely believed that this act destroys the soul of the invested sorcerer, and investiture is considered the most horrific fate a sorcerer can suffer. Some say that investiture is addictive, and that those who drink long enough from the well of souls can no longer sustain themselves with mundane food and drink. Every sorcerer has heard frightening tales of predatory archmagi tutoring eager apprentices with the intent of consuming their power, or of hungry liches luring foolhardy sorcerers to their lairs to feast upon them.

To invest another sorcerer, the character must personally deal the killing blow to that sorcerer, either with magic or by hand. When this is done, the sorcerer may attempt to consume the victim's power. Make a Sorcery skill check with a difficulty equal to the target's Willpower. If you succeed, you have successfully invested the doomed target. You gain one point of permanent Strain, plus one point for every skill rank by which their Sorcery skill exceeds yours (investing a more powerful sorcerer is far more difficult, but the reward is much richer). In addition, you gain a pool of temporary Strain equal to the target's Strain threshold. This Strain may only be used to cast spells. When Strain from this pool is used, it is permanently gone until another target is invested. A sorcerer may hold temporary Strain equal to 5 times his Willpower score.

This is nicely done. I really like the note that Corruption can be concealed with further magic; pushing players down that self-defeating downward spiral is always great fun.

10 hours ago, Direach said:

At each rank of Corruption, there also manifests a physical or mental affliction, chosen by the GM. Generally this is minor and easily concealed at the lower Ranks, while at Rank 4 or 5, the character is unmistakably Corrupted (and may no longer appear human). This can have additional penalties akin to a Critical Injury, or it may be purely cosmetic. Occasionally, the results are helpful (if grotesque), such as a long eyestalk emerging from one's shoulder, or one's fingers being replaced by a bundle of dexterous tentacles.

have you looked at the warhammer 3rd edition rules ?

it uses mutation cards.

Cool concept.

This reminds me of the Dark Sun campaign setting for AD&D. Powerful magic users became more and more physically distorted while simultaneously taking on the role of demi-gods, able to grant spells to acolytes.

Updated with flavour text, new magical maneuvers, and rules for devouring the souls of enemy sorcerers to steal their power. Who doesn't love to do that?!

how does one protect oneself during Assensing, if it is not possible to use Ward during Assensing ?

Nice changes! I believeit would receive more attention if you would put this on a pdf.

3 hours ago, Terefang said:

how does one protect oneself during Assensing, if it is not possible to use Ward during Assensing ?

You don't, that's why you are very careful about when and where you use it. There are very few cities in this setting, so generally it's safe to use the ability out in the wild, but whenever you extend your senses into the unseen world, there is a chance you will be noticed. Although arguably, you protect yourself by having allies present who can defend you if any threats show up, or by being aware of the danger and not using the ability for very long.

There is a risky practice that sorcerers can use called "drumming". Drumming is making your presence known by using strong magic, or otherwise drawing attention to yourself, in order to lure an enemy sorcerer to you, so that you may attempt to trap or kill them. Obviously you need to be very confident in your own abilities to do this successfully.