Plains

Flux Channeler

Whenever you cast a noncreature spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Leori, Sparktouched Hunter

Flying, vigilance
Whenever Leori, Sparktouched Hunter deals combat damage to a player, choose a planeswalker type. Until end of turn, whenever you activate an ability of a planeswalker of that type, copy that ability. You may choose new targets for the copies.

Deepglow Skate

When Deepglow Skate enters, double the number of each kind of counter on any number of target permanents.

Mystic Monastery

Mystic Monastery enters tapped.
{T}: Add {U}, {R}, or {W}.

Mountain

Command Tower

{T}: Add one mana of any color in your commander's color identity.