Sayori, Bundle of Sunshine

Sayori enters the battlefield with a number of Happiness counter on her equal to the amount of
time you chose Sayori this game.
At the beginning of each player's upkeep, that
player gains 2 life for each Happiness counter on permanents they control.
Whenever an opponent casts a spell, move a Happiness counter from Sayori to a permanent
you don't control, then if Sayori has no Happiness counters on her, exile her then return her transformed onto the battlefield under
her owner's control.