Nozdormu the Timeless is a 4 Mana Cost Legendary Paladin Minion Dragon card from the Descent of Dragons set!
Battlecry: Set each player to 10 Mana Crystals.
Nozdormu the Timeless Additional Information
The card only changes MAXIMUM Mana Crystals, not your current Mana Crystals. So if you play it on T4, you will have 0/10 mana left, and your opponent will start their turn with 10 mana. (Source)