Serum Powder

{T}: Add {C}.
Any time you could mulligan and Serum Powder is in your hand, you may exile all the cards from your hand, then draw that many cards. (You can do this in addition to taking mulligans.)

Armageddon

Plains

Endless Horizons

When Endless Horizons enters the battlefield, search your library for any number of Plains cards, exile them, then shuffle.
At the beginning of your upkeep, you may put a card you own exiled with Endless Horizons into your hand.

Barren Glory

At the beginning of your upkeep, if you control no permanents other than Barren Glory and have no cards in hand, you win the game.

Mageta the Lion

{2}{W}{W}, {T}, Discard two cards: Destroy all creatures except for Mageta the Lion. Those creatures can't be regenerated.

Akroma's Vengeance

Destroy all artifacts, creatures, and enchantments.
Cycling {3} ({3}, Discard this card: Draw a card.)