Early game · first 8 minutes
Leave Scrap Grenade's repeated blast areas and keep a dash for shaking off Rat Swarm. Pressure Rat King with a bishop from cover instead of extending gunfire while his rats reduce your bullet resistance.
Solomon vs Rat King
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Mid game · Walkers
Stop shooting Rat King while Royal Pestments reflects bullets. Attack him with your pieces and use Kingside Knight before he reaches you with gunfire; do not rely on one large hit to break his upgraded armor.
Late game · Patron
Back away as Rat King advances with his banner, and spread out before he slams his banner down. Place your pieces across the routes his team needs to use; the banner grants slow immunity, so do not rely on slows to stop them.