We should probably stop posting these in this thread. Maybe it would make for a good game thread of its own. Post a randomly-generated card, the next poster has to try and salvage it into a reasonable design.
There's a web page somewhere that does that... the results are almost always absolutely terrible and/or broken, but if you're persistent you can occasionally salvage an interesting idea from the mashed-up nonsense.
The point of the card was to be a black "flicker" card that goes through the graveyard instead of through exile. I believe I sort of got Turn to Mist and the new Cloudshift card mixed up in my head when costing it, but I'm happy with it as it is. I like the idea that the creature just sort of pops into the grave then steps right back out. I'd be happy with "flickering" back in at end of turn, but forgot to consider that when I'd made the card.
The biggest problem I have with the "anti-tribal" mechanic you used is that it isn't a "positive" goal to meet (turning on once you've met a particular goal) but a "negative" one (it will turn on unless you do something that it tells you not to do). I don't know many people who would naturally be excited to build a deck based around not duplicating creature types, either; tribal effects build on people's natural tendencies to want to group together similar things. A mechanic that encourages you to fight against a natural tendency is not as good a way to get people to enjoy it and want to have fun playing with it.
Tribal is a very popular mechanic, so "anti-tribal" doesn't seem like it would go over that well. Rewarding you for diversity among your creatures is an interesting concept, but would probably be implemented better as something counting the number of creature types among creatures you control, rather than specifying there not be any duplicates.
I love Oculus's card today. That should be in print.
Wow, I somehow managed to misread/skip over that one when looking at today's submissions for voting. I won't change my vote, though, that doesn't seem fair, but I will second that it seems like an excellently designed and elegant card.
Edit: For a name, though, I think I'd prefer "Corpse Claim." Like a necromancer has reserved the creature's body for their personal use.
I might entertain such an idea, if it strikes my fancy. Though I'd probably do that no matter what my score was. I had a handful of Bastion-inspired cards last month after I finished that game, for example.
I had actually been thinking that instead of a keyword that ability should have been tied to creature type. It would have been better if the creature was a Zombie Mutant and put counters on non-Mutant creatures. Very similar result, but it interacts with a few more cards that naturally have the Mutant type or can manipulate creature types (and gives you more flexibility with different kinds of "radioactive" abilities).