If enough creatures die during a single turn, it transforms into Sephiroth, One-Winged Angel, the final major boss of FF7
Kamigawa: Neon Dynasty is no different, and it provides an assortment of powerful cards to tantalize all the blue mages out there
Karmic Guide dying just means it's in your graveyard ready to be reanimated again
Rhystic Study Rhystic Study is arguably the best enchantment in Commander, and probably the best card to run in a multiplayer game
Of course, Boromir can also sacrifice himself to give creatures that you control indestructible until end of turn a nd make the Ring tempt you
Roshan, Hidden Magister Theres been some interesting support for face-down creatures lately, first the new disguise mechanic from Murders at Karlov Manor and now with Roshan, Hidden Magister and its ability that changes your face-down creatures into assassins with menace