Early game · first 8 minutes
Use Barrage from beside cover to damage Rat King and build your damage bonus. Save Flying Cloak to move away when he sends rats and starts shooting.
Pocket vs Rat King
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Mid game · Walkers
Use Enchanter’s Satchel as Rat King starts to slam his banner down. When you leave the suitcase, send Flying Cloak toward cover and teleport away.
Late game · Patron
Use Affliction on enemies gathered around the banner, then leave with Flying Cloak. Shoot low-health enemies from cover; Affliction cannot finish them by itself.