When Ukkima leaves the battlefield, it deals X damage to target player and you gain X life, where X is its power
While its generally better to find a card you can cast immediately after tutoring so your opponents have less time to plan around you, sometimes the threat of a board wipe like Damnation or a counterspell like Cryptic Command will convince opponents to play a little more cautiously, giving you more time to set up for an even bigger play down the road
I really like the fact that it channels EVERY era of turtles, from classic comics to iconic IDW stories, morning cartoons to NES games, and every movie good or bad
There are lots of ways to get your permanents back from the graveyard
Because hes just really freaking good
It also avoided the rampant balance issues that plagued some of the sets after it, keeping the power level at a reasonable and enjoyable level