Rentol, Pursuer of Knowledge

Haste
Whenever a creature you don't control enters the battlefield or a token you don't control leaves the battlefield, research. (To research, create a colorless Papers artifact token with " {1}, {t}, Sacrifice this
artifact: Scry 2.")
{t}, Sacrifice an artifact: Rentol, Pursuer of
Knowledge deals 3 damage to target creature
or planeswalker.