This is an exile matters set and I think I can do something creative with losing life, but I dunno how to make it cool or matter for a big mythic like this.

Well, I'd think about not making it half. Cards this expensive are allowed to flat our win games; after all, you could have just used a Fireball or a Drain Life instead.

Ok, the ETB ability is ramped up now, but the body still isn't particularly interesting. Any suggestions?

Eight toughness deathtoucher seems plenty solid enough to me.

@Vitenka I could go with a more top-down design and reduce its power to 1, but give it first strike or something. What do you think of that? A 1/8 first strike, deathtouch? It sort of feels more like a wall that way, but the enemy in the anime didn't really move all that much so it kind of fits...not sure if it's mythic material, though.

Ok; this is ALREADY stealing 5+ life per opponent in set (assuming they go for memory; it being the set's thing) and is very hard to kill and kills off whatever blocks it?

I don't expect first strike would make a huge amount of difference, few opponents will be able to muster 8 points of first strike.

At 1 power it would only block (or the opponent would just leave it unblocked). Which might be a bit of a dull reward for an ETB creature. At 4 power, the opponent is likely to block it (and you already stole life ...)

Maybe Power equal to cards in exile? Though that might be too good.

Personally, I'd leave it unless it's really not fitting your flavour.

I think the life swing is enough to make this card distinctive, it would be fine with typical "big black mythic creature" stats (typically big and flying or trample).

I don't think there's a need to make the stats more unique, but I don't know anything about the character -- if there's anything that would be appropriate, I agree it would be better. And I agree making it reasonably able to attack is good.