This can do some gnarly stuff with a fog! Feels like this would really gum up a board. Perhaps the creature tokens that you make should have a "defender counter" rather than just having defender?

Let's say this is your commander or somesuch. What kinds of game plans do you think this sort of deck would have?

I assume it's better to have it enter with a defender counter is for memory issues? Indeed, that's a good point.

Now, the idea* here is this thing really enjoys stuff that triggers upon creatures ETBs, and stuff that wants to use creatures as resource (like, sacrifices, flings or whatnot). Each creature (without defender) can basically produce and extra ETBs trigger, at the cost of gaining defender, and one can prop this further with fogs and 0 powers creatures, which effectively clone themselves upon attacking. Doing all that should incidentally also produce quite a pillow fort, and if some opponents has creatures with good noncombat abilities, this can produce copies, although one can't really have much control on that.

*in reality, there wasn't much though behind the thing, and it's just something that kind of randomly came to mind