Divine Hymn
20% of base mana
1.5 sec cast 6 min cooldown
You recite a Holy hymn, causing the closest 10 enemies within 15 yards to become incapacitated for 20 sec., and heals the closest 10 friendly targets within 15 yards for 348 every sec for 6 sec. Incapacitated enemies take 40% less damage while incapacitated and for 3 sec after the incapacitation ends. Damage caused may interrupt the effect on all incapacitated targets.
All you have to do to stun the entire other team, is to be as close to the other team's square as possible and start casting this 1 second before the arena starts and everyone is incapacitated for around 8(c/d?) seconds. Then you can burst someone down quick. Even if their healer trinkets, any CC they receive will be GG. REALLY useful in 5v5.
GL in arena!