The Star Plague

Enchant Player
At the beginning of the enchanted player's
upkeep, that player loses 2 life. While this player
is enchanted, they cannot gain life and they may
treat any colored mana in a spell's converted
mana cost as Phyrexian mana. (They may pay 2
life instead of the specified colored mana in that spell's converted mana cost to cast that spell.)