Hey, Hydriatus! I read through this and it looks solid, though it could use a little refinement. Valentyn seems like a character that's got potential, but he's stretched a bit thin at the moment. I think his strongest angle is his paranoia/self-preservation. That's something I find interesting and, if played right, could make for some cool stories.
Now, here's the thing about color identities: Don't worry about them.
No, really, just forget about them when making a character. Don't even think about it. Just make a character. You want someone with a sword who can manipulate earth? Sure, do that! Fire mage with a propensity for steam? Done! How about a death mage that ONLY kills plant life? Weird, but ok! And maybe the death mage just HATES forests because he grew up on Zendikar and his family got eaten by native flora or something, and so he has a healthy respect for civilization that is capable of beating back encroaching nature. Maybe he really respects research into various anti-plantlife methods, or maybe he's just fueled with rage.
The thing about this character, is that he could be ANY of the colors, sure - but it's the Black that stands out the most. But you only really come to this conclusion after you see the whole picture.
See, if you try to put your character into a box before the character is even on the page, you're doing yourself - and your character - a disservice. Like you said, writing within a system is important. But to do that, all you have to do is WRITE and then make the system work for you. There aren't many hard and fast rules in Magic, and I'm not really into discussing color philosophy endlessly, but what I can say is that Valentyn Mason? He's Black. Very, very Black. If I had to choose a second color, I'd choose Red, but White also works, like Raven suggested. If you REALLY want all three colors, you could. I think he works like that.
But since his best trait is self-preservation, yeah, definitely Black. So, work towards his strengths!
EDIT: Oh, I'd also like to address this:
Quote:
Then since we're discussing misconceptions - how the heck does a regular game of Magic look like lore-wise? How does summoning creatures work? Attuning yourself to land? What's the difference between a battle using "standard" and "EDH"...? Actually, nevermind, those questions are more story related >_<
There is no 1:1 relation between individual games of Magic and lore. It just doesn't work, it really doesn't. I mean, you can have phyrexians and mirrans fighting on the same side of a battlefield. Like, don't try to make sense of it because it doesn't make sense. Just remember that the lore and the game are divorced from one another. There was this whole custody battle...