Yoooo that horror phantom though!imagine him being normal as hell to his s/o(normal ego wise)and say his s/o gets threatened by someone with a weapon (another ego? A poor human that's gonna be murdered?) And he drops the human skin around them for the first time right there to absolutely destroy the threat before realizing what he did. Staying as still as possible as his s/o slowly comes up to him and puts a hand against his "cheek" only to hear him all but purring. He's relieved they didn't run
Horror!Phantom would be terrified of scaring you away from him. But he would be so protective of you after that day.
Anytime an ego comes near you, he sheds his facade (if they're away from prying eyes) and is instantly in attack mode. Unless the ego states otherwise and gives you and Phantom a reason to trust them.