Robes of Tirisfal

(2) Set: While above 75% mana, your spells deal 3% more damage.

(4) Set: Arcane critical strikes increase your spell haste by 6%. Fire critical strikes increase your spell critical strike chance by 6%. Frost critical strikes increase the damage of your critical strikes by 4%. Each effect lasts for 8 seconds and they have a 5 seconds shared cooldown.