Kaltan, the Last Merfolk

When Katlan enters, choose a color.
Whenever a player taps a land for mana, it it isn't a basic land, Katlan deals 3 damage to that player.
Whenever a player plays a nonbasic land, Put a -1/-1 counter on Katlan.
Whenever you tap a basic land of the chosen color, add one extra mana of that color.

"Once, our songs called the rain. Now, they only echo over poisoned tides."