(Not to be confused with a Occultic alter, an area of worship for false Gods and an area of Sacrifice.)
Satan and his demons, like with many guises they've found to use and abuse in order to decieve people, have been found using Multiple Personality Disorder (MPD) to their advantage by pretending to be another personality in the person. Alters are something of an anomaly in the Demonic Realm,
Many of those who are aware of them often are accused of heartless cruelty and emotional abuse when casting them out. Through even in the Bible this is the same way Jesus cast these demons out by dealing with these so-called "mental disorders". Even the most broken people in the Bible such as the man living in the tombs (Mk. 5:15; Lk. 8:35) were healed and freed when Jesus cast out the demons.
For more information on how demons decieve people through appearance or senses, see Demonic Guises.
How to Tell if a Alter is DemonEdit
Make the alter say "Jesus is Lord." Overtime the alter will weaken, get tired, or go insane which involves swearing or even on rare occassions attacking the exorcist. Once this begins the Exorcist most likely has found an alter, through it should be remembered that some people with MPD do have their other selves hating Jesus through this is rare. Many times the demon who takes the place of a so-called other self tries to convince the Exorcist that they are indeed just the other self of the person, these demons often are successful in their ways with Exorcists. Than the Exoricst lets them leave without casting out anything, leaving the Devil still owning the oul of the person and eventual death of the demonically possessed.
 A Minister teaching about the alters of demons, using multiple personality disorder (MPD) to its advantage.