Slingsby the Scorcher is one of the Higgledy in Ni no Kuni II: Revenant Kingdom who can be found in Broadleaf. If Evan brings Whole Milk to the Higgledy Stone located on Dynafloor No. 3, Slingsby the Scorcher will join him.
Slingsby the Scorcher is necessary to complete Side Quest 112: Healing Rifts with Higgledies.