Donut's tiara, whose advanced targeting skills let her hit anything in line of sight.
When the Princess Posse designed The Nest, the plan was a sniper tower to help Donut zero in across the battlefield. It turned out to be unnecessary: with her tiara's advanced targeting skills, plus her elevation and her Deathbed Hellcat class, all Donut needs is line of sight to apply her sniper skills to any long-range spell.
That freed the tower's synergy for Atrocity-Class Spells. In this chapter the tiara's targeting delivers four dead War Mages and a graze on Prince Stalwart as he teleports out of a tank, all via Magic Missile.
A tiara worn by Donut, granting advanced targeting.
The targeting system that made a dedicated sniper tower redundant.