Not only can he reanimate any creature from your graveyard, no strings attached, but hes difficult to remove, too
That means were going to have to be more creative in not just how we decide to close out the game can we even win with combat damage, or do we need to figure out some combo kills but also how the heck we survive the early and midgame when our board presence consists largely of overcosted and underpowered creatures
That means well be getting a whole new set of legends to incorporate into the game, and new mechanics too
Each teammate will help in different ways to achieve your goal: build up +1/+1 counters and grow your creatures into the worlds most fearsome fighting team
As such, spells like Rampant Growth, Cultivate, and Deathsprout wont be as good as usual
That being said, it does come at the additional cost of two life