Whenever you cast a noncreature spell, put an oil counter on this creature.
Remove three oil counters from this creature: Draw a card. Then you may discard a nonland card. When you discard a card this way, this creature deals 3 damage to target creature or planeswalker. Activate only as a sorcery.
You don't choose a target for Serum-Core Chimera's last ability at the time you activate it. Rather, a second "reflexive" ability triggers when you discard a card this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.