Like most Magic: The Gathering cards, the value of Mountain depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (March of the Machine)
Even if the enemy manages to deal with them, the Thinking of You ability turns their defeat into a massive advantage by sending all involved cards straight into the user's inkwell face down and exerted
I could probably split each of these tiers into two or three more if I wanted to
Lightly Played Foil (LP Foil) cards maintain a decent foil surface with only minor imperfections
This can be extremely disruptive to decks that need pieces of their combo to activate from the graveyard
Well, this guy has "betray" right there in the name, so he's gotta get passed around the table, right, and he's really hard to kill