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.)

Forest

Lost in the Woods

Whenever a creature attacks you or a planeswalker you control, reveal the top card of your library. If it's a Forest card, remove that creature from combat. Then put the revealed card on the bottom of your library.

Sasaya's Essence

Whenever a land you control is tapped for mana, add an additional one mana of any type that land produced for each other land you control with the same name as it.

Sasaya, Orochi Ascendant

Reveal your hand: If you have seven or more land cards in your hand, flip Sasaya, Orochi Ascendant.