BIOGRAPHY - page 4
Having found the body he always wanted, Proteus attempted to return home to Earth-616, but Heather Hudson managed to use the Panoptichron's systems to trick him mid-transit into appearing on Counter-Earth, the artificially created duplicate of Earth revolving on the opposite side of the sun. As he did with the Squadron Supreme, Proteus befriend the heroic Young Allies when he first arrived in order to play them against the Exiles when his pursuers caught up with him. Once Longshot and his luck shield were dealt with, Proteus revealed his true intentions and turned on the Allies. He amused himself by raising Atlantis to the surface and claiming Queen Dorma's crown for himself. This proved to be his undoing, because the Exiles had finally discovered a means of stopping him. 
By taking Behavior Modification technology from the Squadron's world and hiding it inside the crown, they reprogrammed Proteus's thoughts so that he could only access Morph's memories. Proteus' energy form was now trapped inside a body that wouldn't break down, while Proteus's mind was convinced that he really WAS Morph. And, although they were understandably leery about having one of their greatest threats among them, the Exiles allowed "Morph" to continue operating as part of the team, playing along with his brainwashing to keep Proteus from realizing the truth. [Exiles (1st series) #81-82]
For all intents and purposes, Proteus, as Morph, became an active member of the Exiles for several months and over dozens of worlds saved or righted by their intervention. Even so, the Exiles were always on the lookout for signs of Proteus's original personality resurfacing. 
Heather Hudson became particularly concerned when she realized Proteus had no reaction to the metal crown used to reprogram his mind, meaning Morph's body somehow insulated Proteus from his one weakness. When the Exiles fought a version of the Hellfire Club, Emma Frost nearly unleashed Proteus from Morph's consciousness with her telepathic powers. Fearful of a regression, the Exiles began keeping Morph asleep between missions, using the B-Mod device to routinely reinforce his surface personality. [Exiles (1st series) #83-89] During the chaos surrounding the recruitment of Psylocke-616, however, Morph was shaken awake and the B-Mod headdress was damaged. The next several missions struck one after another, leaving no opportunity to re-imprint his programming. [Exiles (1st series) #90-99]
"Morph" continued to fight on the side of the Exiles for some time, but occasional glimpses of Proteus' true personality would seep through. [X-Men: Die by the Sword #3-4] Eventually, Morph had a full relapse into Proteus's personality during a conflict with the Maker, an evolved Cosmic Cube manipulating people like puppets. Despite the reversion, Proteus still felt the inexplicable urge to help his fellow Exiles stay alive and fight off the Maker's machinations. 
After some confusion, Proteus realized that the original Morph still existed within his mind, and had not been assimilated like his other hosts of the past. The two souls reached an accord, as Proteus recognized that (through Morph) he had finally found a place where he belonged, and Morph's compassion and empathy had affected him more than he realized. Working together, Morph and Proteus defeated the Maker and saved the Exiles. They began acting as a symbiotic mind, both personas seamlessly transitioning between one another while interacting with others. [New Exiles Annual #1]
Some time later, though, Proteus and Morph were completely separated by forces beyond their control. 
The crystalline structure of the Panoptichron reacted to the Exiles' continued presence in its walls by absorbing them into the crystal itself. The Crystal Palace somehow differentiated between Proteus and Morph, absorbing the former into the crystal walls while leaving the latter unscathed. [Exiles (2nd series) #6]
[Note: The fate of Proteus-HoM is uncertain. Several of the Exiles trapped in the Crystal Palace (Sage, Sabretooth-AoA) have resurfaced in other stories, indicating that those Exiles were eventually released from the crystal wall unharmed. Linearly speaking, Proteus resurfaced on Earth-616 shortly after the story where Proteus and Morph were separated at the Panoptichron. So either Proteus-616 was restored as dispersed energy on Earth-616 after the House of M reverted to normal and Proteus-HoM is still out there in the multiverse, or Proteus-HoM was returned to Earth-616 after being separated from Morph and reverted to his original identity and memories in the process.]