Jun 6, 2017
Me and a friend were discussing Drain Power and we were wondering how it interacts with cabal coffers, mana confluence, signet lands, etc. Anything that requires paying a cost to activate the mana ability. Does it force the player to pay that cost if able? I didn't think so because from what I know you usually can't force an opponent to pay costs.
Your opponent has to pay the cost if able. Since they’re tapping lands for mana, it’s unlikely that there will be many scenarios where they won’t be able to activate a mana ability of a specific land. Note that they get to choose which mana ability is activated, though.