Bael, Sovereign's Mistake

Deathtouch
{b}: Sacrifice either other target Legendary creature
you control, or target Planeswalker, exile this card
and return it to the battlefield transformed.
For the rest of the turn, creatures you control have Synthesize {3}. (Synthesize a creature by
exiling it under this creature. The creature with Synthesize gains either: a +1/+1 counter, or a
Keyword from the creature exiled beneath it.)