Secret Lair x Ghostbusters: Slimer

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it.) Mill five cards, then return a creature card from your graveyard to the battlefield.

{X}, Sacrifice this enchantment: Destroy each artifact, creature, and enchantment with mana value X or less.

As The Mimeoplasm enters, you may exile two creature cards from graveyards. If you do, it enters as a copy of one of those cards with a number of additional +1/+1 counters on it equal to the power of the other card.

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.) Counter target activated or triggered ability. If a permanent's ability is countered this way, activated abilities of that permanent can't be activated this turn. (Mana abilities can't be targeted.)

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.