Alecto is one of the three Fury Sisters. She is sister to Megaera and Tisiphone.
After Megaera has been defeated a certain amount of times, Alecto and Tisiphone will begin appearing, randomly replacing her at the end of Tartarus. Alecto does not appear in the House of Hades after she has been defeated.
'...Each of the ancient Fury Sisters is preoccupied eternally with tormenting a certain swath of moral crime, and Alecto enjoys the broadest swath of all: those who, during their mortal days, committed wrongful acts at the behest of their impulsive passions. With that being the case, I see it somewhat as a miracle that I myself avoided her barbed whip here in the Underworld; and I am thankful for it, for Alecto's reputation paints her as a being best given the widest possible berth. That she appears to be on questionable terms with her own sisters, and is not permitted in the House of Hades due to profane acts of insubordination long past, perhaps is all that needs be said of her for now.'
For quotes and dialogue regarding Alecto, please refer to Alecto/Quotes.
Alecto can appear as a boss in Tartarus. For more information on the boss of Tartarus, see The Furies.
Unlike Megaera, whenever Alecto is defeated, she is not taken by the Styx but instead scatters into a flurry of red bats. This reflects how she is not allowed in the House of Hades.
For additional information on Alecto that does not pertain to Hades, see Wikipedia's article: Alecto