Skaarn, Noble Thief

First strike, deathtouch, Lawful Good (skaarn may only deal combat damage to a creature if the damage that that creature would deal to Skaarn would kill Skaarn)
Skaarn cannot be blocked by walls.
Whenever target player would cast a spell, you may tap Skaarn, if you do, counter that spell, add {x} to your mana pool where X is the countered spells converted mana cost.
I've seen that guy somewhere before, but I don't know where.