The Elder Scrolls

(If you have a Birthsign in your opening hand, you may begin the game with it on the battlefield. You can only control one Birthsign at a time.)
Lands you control have ": Add to your mana pool" and lose all other mana abilities.
Mana doesn't empty from your mana pool as steps and phases end.
Whenever an opponent casts a spell, add one mana of any color to your mana pool.