Dragon Age 2: Act 2: Repentance: Nightmare Level Mage.

Sebastian sees strange goings on in the Harriman's bedroom...involving feathers. So heads for the basement to cool down. Only it gets hotter.
Key points to remember when using Gravitic Ring. Make sure your party members don't run into it on autopilot, like Aveline almost does. It screws up combat quite often, and your party member gets locked out..
Likewise with Archer's Lance, if left to tactics, party members will often be standing, or run into the line of fire and die. Check before it fires and move them using Hold. ( Aveline and Ander's may well have been wiped out with the second Rage Demon had I not done so as all three were more or less in a straight line to Sebastian )
And with the Archer's Lance and Brittle combo, it often pays to reposition before firing for the full advantage. Not always possible given the Brittle may time out before you move to the sweet spot. But here Sebastian is close enough to do the double on both Lady Harriman and Allure.