Sometimes it was more like six: Dark Confidant made you lose 6 life if you revealed it
Mana Crypt is just one of the best mana rocks ever, Jeweled Lotus made expensive commanders like Tivit, Seller of Secrets and Niv-Mizzet, Parun far easier to play, and Dockside Extortionist was a hideously broken ritual that was central to many infinite combos with cards like Temur Sabertooth and Barrin, Master Wizard
The one you see today won't be the last one
(A creature with menace can't be blocked except by two or more creatures.) Midnight Mayhem affects only Gremlins you control at the time it resolves, including the Gremlin tokens it creates
This deck is remarkably powerful and features a number of powerful creatures, planeswalkers and synergies
instead, sell them while demand is relatively high