Kolata, Mana Thief

Flying
Mana doesn't empty from your mana pool.
Whenever an opponent would add mana to their
mana pool, that player may pay 2 life, if they
don't, add that mana to your mana pool instead
of theirs.
"Just as you think you can win, that pesky dragon
comes along and steals what you've gained!"
-Wigen, priest of the Manaliths.