informal or slang terms for mentally irregular; "it used to drive my husband balmy"

Insane. As in, "The winds of Pandemonium'll drive a body barmy if he stays too long." Barmies are insane folks, especially those in Sigil, who've been "touched" by the impossible bigness of the planes.

nutty [colloq.], crazy, irrational

adj. Strange or very silly. Often said in jest amongst friends

ornamental collar of the tsar's official robe

Full of barm or froth; in a ferment.

marked by spirited enjoyment