Keeper of Progenitus 
Creature — Elf Druid
Whenever a player taps a Mountain, Forest, or Plains for mana, that player adds one mana of any type that land produced.
Legality
standardNOT LEGALpioneerNOT LEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL