Dragon Age 2: Sky Horror and Cultists: Nightmare Level Mage.

Ok Chaps, chocks away.
There is no way we can allow these guys to get airborne, so do your duty, for Thedas. It's time to clip some wings.
Yep, this one is a tough one and in great part is down to critical timing, hitting the Sky Horror the instant he begins to teleport in with serious DPS will immediately knock him back out again. Sometimes though even that split timing won't work and he will rain on your parade heavily with instant death via purple cloud. The moment he appears. Luckily not this time.
Good use of Dispel Magic here from Anders helped prevent drastic death for Tallis from the Sky Horror's aura in the second phase, it was close though.
All level 26 here, with no spirit runes or warding on anyone here, except for Aveline and her Elemental Aegis.
Music, what else. 'Aces High' aka 'The Luftwaffe March'.

[@AzureKani]

Best way do with this fight is to force the Sky Horror to retreat asap otherwise he's gonna spam his AOE spells. Do this by using a spell like Winters grasp or Petrify to Brittle him then have Tallis use Drop dead on him, if you have another rouge in the party, use twin fangs along with Drop dead. This helps tremendously.

[@slan7]

Lol, marching band music. Great job at defeating this mini-boss. He's really tough and his AOE spells are KO me in seconds. I know this video is more than a year old but do you have any suggestions in defeating this enemy? This battle would be much easier if there wasn't a barrier blocking the rest of the map.

[@zirize]

Actually you don't need any magical resistance runes for this battle.
It's a kinda tutorial battle for Tallis's special talents, Cover-Up and Cloak.
If you use these talents properly, you can completely make the mage slience.
Timing is not easy, though.