Master the Theory
From Archon Arcana
Master the Theory • Logos • Action • Rare • Play: If there are no friendly creatures in play, you may archive a card for each enemy creature. • Artist: Sean Donaldson • Card Number: AoA (148), WC (169), MM (106)
Commentary
At the 2019 Richmond Vault Tour, it was ruled that when Master the Theory is played and there are no friendly creatures in play, the Active Player may archive any number of cards up to the number of enemy creatures in play.
Source: Keyforge Vault Tour: Richmond - Round 4