The 999 Second Harold Stall | RS-8 Skadeknights 

RS-8: 3 Skade-illustrated operators only
Not the worst stall I've ever done, but certainly the longest I've done with the Skade squad. Executor Alter can kill literally everything else in the map, but Harold requires some special attention. With Specter Alter and Phantom S1, both of Harold's phases can be infinitely stalled due to Specter's two forms being able to tank attacks long enough for Phantom to block during the doll's duration. Of course, this takes long enough that I run into the 999 second time limit for the blizzard, which makes managing Harold's HP in phase 2 a lot easier. I probably could still win with an infinite duration blizzard, though the clear would've been longer than 14 minutes as a result.
Music:
Play with Burdenbeasts (RS battle theme)
First Crevasse on the Frozen Lake (Harold boss theme)