Alright, so one of the adventures I plan on running with my group is Hand of Corruption. However, everyone in my group are space marines.

What ideas do you have for infiltrating them onto the planet? I kind of liked the "Inquisitor" idea, but I need a human to pull that off (or I guess I can create an NPC and have them come across him). Are there any other ideas you might have?

HoC is extremely difficult for marine characters. Maybe you should think of asking your players to create some human PCs for this one?

What makes it so difficult? (Besides the blending in, of course?)

They are pretty excited about what they have, so at most I was thinking about creating an NPC they could use to get them in as an Inquisitor with the space marines acting as an assigned body guard. I might save this adventure for way later, though.

Here are my plans: Tutorial "mission" for each of them separately to explain how they get to where I will have the whole group start together (the Broken Chains ship), and I will use that to introduce combat to each of them. (This allows me to introduce each one and play on their stories separately).

After that, they will do Broken Chains, and in the end, they will get to keep that ship. However, the ship itself lacks a crew and anything significant. From there I will create a freeform world for them (using the setting, of course), with their first goal to get their ship operational, fitting in the book adventures that I have as a means to doing those things.

Once their ship is operational, I'm going to do a semi transition to Rogue Trader, where they have a ship, and now their goal is to fulfill their character ambitions and such. They can do whatever, but I will do what I can to guide them into a story that I will develop.

Also, these players are awesome roleplayers and good friends, and at least two are having characters that worship the polar opposite. One is going to follow Khorne, the other Tzeentch, and both plan on disrupting each other (though covertly).

Actually Khorne and Tzeentch are not opposites and even work together quite often though they have their "little" differences.

So Khorne may not like Sorcercy if it comes to combat and scheming for he honors martial prowess and honesty, that is for sure, but his hatred for Slaanesh and what it stands for is surpassed by nothing.

Well the tzeentch guy could make up a delicious chaos ritual that creates an illusion that makes everyone think your CSMs are regular humans. Tzeentch would love it. It would also put a bit of a crunch on them as they have to find wish the mission before the illusion dissapates.

Actually Khorne and Tzeentch are not opposites and even work together quite often though they have their "little" differences.

So Khorne may not like Sorcercy if it comes to combat and scheming for he honors martial prowess and honesty, that is for sure, but his hatred for Slaanesh and what it stands for is surpassed by nothing.

He hates them both, and both of them are "opposed." All chaos gods have worked together and made alliances at times, too. Also several other adventures talk about exactly what I said, "Where one player dedicated to Tzeentch might want to search a library for forbidden knowledge, another dedicated to Khorne might want to destroy it."

Well the tzeentch guy could make up a delicious chaos ritual that creates an illusion that makes everyone think your CSMs are regular humans. Tzeentch would love it. It would also put a bit of a crunch on them as they have to find wish the mission before the illusion dissapates.

I love this! It will be interesting to see the sorcerer try and convince the Khorne follower to do something so low as to hide himself!

He hates them both, and both of them are "opposed." All chaos gods have worked together and made alliances at times, too. Also several other adventures talk about exactly what I said, "Where one player dedicated to Tzeentch might want to search a library for forbidden knowledge, another dedicated to Khorne might want to destroy it."

Khorne has a rivalry with Tzeentch and he despises his schemes and hates those that use psycic powers in favor our their personal strength in combat. Though WH40k lore made it pretty clear that his hatred against Slanesh is of another quality. Tzeentch and Khorne are opposed but Slanesh and Khorne are opposites.

I am just referring to direct GW and BL source material and I am not arguing that there are no tensions between Tzeentch and Khorne. I am only arguing that these two are not the polar opposites as you stated them to be for in fact it is Slanesh to Khorne and Nurgle to Tzeentch.

He hates them both, and both of them are "opposed." All chaos gods have worked together and made alliances at times, too. Also several other adventures talk about exactly what I said, "Where one player dedicated to Tzeentch might want to search a library for forbidden knowledge, another dedicated to Khorne might want to destroy it."

Khorne has a rivalry with Tzeentch and he despises his schemes and hates those that use psycic powers in favor our their personal strength in combat. Though WH40k lore made it pretty clear that his hatred against Slanesh is of another quality. Tzeentch and Khorne are opposed but Slanesh and Khorne are opposites.

I am just referring to direct GW and BL source material and I am not arguing that there are no tensions between Tzeentch and Khorne. I am only arguing that these two are not the polar opposites as you stated them to be for in fact it is Slanesh to Khorne and Nurgle to Tzeentch.

Yeah, that was bad wording on my part.

Well if all of your marines have the minion talent, they could try to send those down to secure a method of infiltrating the complex.

Alright, so one of the adventures I plan on running with my group is Hand of Corruption. However, everyone in my group are space marines.

What ideas do you have for infiltrating them onto the planet? I kind of liked the "Inquisitor" idea, but I need a human to pull that off (or I guess I can create an NPC and have them come across him). Are there any other ideas you might have?

As far as penal colonies go, St Annards is ridiculously small scale and doesn't justify the insane fleet presence above it in the slightest. If you tweak it so it's less of an adventure author's railroad and more befitting of its excessively minor status (which is probably the only explination for "haven't found necrons yet" that makes sense...), you can flat out marine-style it.

Alternatively, if they do want to go subtle, they need loyalist marine gear. Let them figure out how to get it. The easiest way is to lure the inquisition into a trap and blam some, but that MIGHT get you facing off against grey knights. That's the downside there. Alternatively, hitting a recruitment world while the chapter's away elsewhere might be a good idea.

Just make someone forge a paper about them inspecting the planet, get a repaint and go to town! Who's going to question space marines? Say they're looking for recruits or something.

What makes it so difficult? (Besides the blending in, of course?)

Besides the blending in - nothing.

Except that you are doomed to fail without blending in somehow.

You could go Alpha Legion style with the group pretending to be loyalist space marines, even painting their armour and everything. As Ghaundan said the authorities are going to be very nervous questioning space marines, especially as they don't know where the rest of the chapter may be (as long as the players don't do anything too obvious or stupid).

The Inquisitor idea sounds good too and can be used in conjunction with my first idea. You don't even need to have an inquisitor PC, you could have an astropathic communication sent to the penal colony from the "Inquisitor" telling them that he suspects Chaos taint on the planet and that he is sending in his trusted space marine unit to investigate. Of course these space marines are to be treated as if they had his authority and every courtesy should be given to aiding them in their investigations of the matter at hand......

You could. But you need to be really convincing with little to zero mistakes allowed.

If done right, this could turn into a middle finger to anyone believing that Legionnaires in Black Crusade are unfit for socializing.

Definitely agree, although when you are on an Imperial Penal colony with a massive Imperial Guard/Navy and Adeptus Arbites presence you probably can't afford to make to many mistakes whether you are a CSM or human.

Certainly if you play the actual Alpha Legionnaire or a (subtle and covert) Dark Apostle you have the potential to cause quite a lot of strife in Imperial territories without even firing a shot. Admittedly these are advanced stereotypes, but you can even gear your standard stereotype space marines with more social skills. In fact when I played Deathwatch (my least favourite of the lines) I actually found quite a lot of freedom to play scientific or social characters because they were automatically good at combat so I didn't need to focus building them up in that area. Probably a moot point though since the characters have already been created.

I have both seen and played social CSM. That whole thing about them being antisocial is nonsense, unless you like your CSM being socially atrophied murder-monsters.