Rin, Soulkeeper

Partner with Ex, Lorekeeper (When this creature
enters the battlefield, target player may put Ex into
their hand from their library, then shuffle.)
Flash, Deathtouch
Whenever another creature dies, you may pay {1}. If you do, draw a card and lose 1 life.
If Rin would leave the battlefield, their owner
may shuffle it into its owner's library instead.