User blog comment:GrimRevenger/Mayu's Room Guess/@comment-115.66.109.119-20160613204407

Expand on a current restriction: a deck can only contain 2 copies of cards containing the name "Arcgain".

Meaning either 2 whitegains, 2 blackgains or 1 of each.

Kek.

Doubt this would actually happen tho.