THE MANIAI (or Maniae) were the spirits (daimones) of madness, insanity, and crazed frenzy. They were closely related to Lyssa, the spirit of mad rage, and the Erinyes.

Theognis, Fragment 1. 1231 (trans. Gerber, Vol. Greek Elegiac) (Greek elegy C6th B.C.) :
"Cruel Eros, the Maniai (Spirits of Madness) took you up and nursed you."

Aeschylus, Fragment 179 (from Etymologicum Genuinum s.v. asalês) (trans. Weir Smyth) (Greek tragedy C5th B.C.) :
"Or reckless madness (mania) from the gods." [N.B. Mania is perhaps here personified.]

Quintus Smyrnaeus, Fall of Troy 5. 450 ff (trans. Way) (Greek epic C4th A.D.) :
"[Ajax went mad when the armour of Akhilleus was awarded to Odysseus, and he slew a flock of sheep imagining they were his Greek enemies :] Thinking that amidst the slain Odysseus lay blood-boltered at his feet. But in that moment from his mind and eyes Athena tore away the nightmare-fiend of Mania (Madness) havoc-breathing, and it passed thence swiftly to the rock-walled river Styx where dwell the winged Erinnyes, they which still visit with torments overweening men."

Ovid, Metamorphoses 4. 481 ff (trans. Melville) (Roman epic C1st B.C. to C1st A.D.) :
"Malign Tisiphone [the Erinys] seized a torch steeped in blood, put on a robe all red with dripping gore and wound a snake about her waist, and started from her home [in the Underworld, on a mission to drive Athamas mad]; and with her as she went were Luctus (Grief) and Pavor (Dread), Terror (Terror), and Insania (Madness) too with frantic face."

Sources:

• Greek Elegaic Theognis, Fragments – Greek Elegaic C6th B.C.
• Aeschylus, Fragments - Greek Tragedy C5th B.C.
• Quintus Smyrnaeus, Fall of Troy - Greek Epic C4th A.D.
• Ovid, Metamorphoses - Latin Epic C1st B.C. - C1st A.D.