Playing creature spells during the declare blockers step isn't terribly useful, for one thing. It's already a really bad Snapcaster Mage even if the ability was upgraded to "any time," but with a restriction like that it might as well just be vanilla.

Yeah, this ability seems silly. Playing then is too late to block with it. And what's the point of an ability whose only use is to be worse than Flash?

oh yeah i forgot about attacking part...

I guarantee you that people will think "your declare blockers step" refers to the step in which you declare blockers on your opponent's turn.

I did when I first read it. It's a cute idea, but unfortunately it isn't very different than "Kickervariant . When ~ enters the battlefield, if you paid the Kickervariant cost, ~ gains haste, and can't be blocked until end of turn."

Maybe the way to do it is to treat these all like Ninjas and give them all a saboteur ability. Furtiveness is even more guaranteed to hit a player than Ninjutsu was, so the costs would have to respect that, but I could see versions of this with saboteur triggers to "draw a card" (cf Ninja of the Deep Hours), unsummon (cf Mistblade Shinobi), etc.

This is a little different to the kickervariant in that the opponent doesn't know about this when declaring blockers. If they're trying to carefully manage their life total, this could be a kick out of nowhere.

Mm. True. But it doesn't really encourage interactivity. It's just a surprise for the sake of being a surprise. That said, I probably shouldn't have claimed it's exactly the same things. It's just the differences between Furtiveness and Kickervariant don't really impress me. It might excite other player that aren't me, though.

Wow. And suddenly it's a boring morph card. Funny how if it weren't for the second U in the morph cost, the second ability, and the +1 power, it would be a cheaper Scornful Egotist.