+2: Search your library for a basic Mountain card, reveal it, put it into your hand, then shuffle.
−3: Koth, Fire of Resistance deals damage to target creature equal to the number of Mountains you control.
−7: You get an emblem with “Whenever a Mountain you control enters, this emblem deals 4 damage to any target.”
Koth's emblem is colorless. Notably, this means that protection from red won't stop a permanent or player from being the target of the emblem's ability, nor will it prevent the damage being dealt. Replacement effects that care about damage from a red source don't apply to it.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.