The thing that sank Dabran the Pirate’s ship Retribution was Degorran, a little-known sea demon of the Fifth Circle. Shemder the Lame, the demonologist aboard the Ethsharitic trader Behemoth who was responsible for summoning Degorran, had been attempting to contact the much less formidable second-circle demon Spesforis the Hunter when he got lucky and brought up Degorran instead.
The invisible servant Tobas called Nuisance was in the castle in the void when Derithon first created it; in fact, it was arguably the castle’s rightful owner until Derithon placed it under several assorted spells of constraint and compulsion, and its abuse of Tobas was as close as it could come to wreaking vengeance for its enslavement on all wizardkind.
And finally, spriggans really are harmless, except in large numbers, but not quite as stupid as Tobas hoped; it took them three years to figure out that the mirror wouldn’t work in the fallen castle and another year after that to drag it somewhere it would work, unleashing the steady supply of spriggans that continued to plague Ethshar from then on.