MØTH!

V1 is majorly feral and was only released from its stasis because of Pharloom's decline; it sees Hornet as only a fuel source at first, and after being dissuaded otherwise at the point of her needle, begins to try and find other fuel sources around the Citadel. You could probably see it doing things like killing enemies to get at the silk inside them, trying to break open the silk spool 'vending machines', etc (which Hornet can pay for to buy it silk, which it will then happily leave with). Positive interactions would raise its friendship with Hornet. Maxing out its friendship with her would cause it to help Hornet with gauntlets around the Citadel and offer reoccurring sparring matches, where it learns from her based on the tools she uses in fights with it.

At some point before that, it would get its claws on a rosary cannon and start wearing rosary strings (for ammo). We bounced the idea of it having a shop with wildly RNG prices because it wants rosaries for ammunition but it doesn't know what currency is.

(When it meets Gabriel the prices become more consistent because he can't stand it overcharging/undercharging.)

Gabriel can be met in Act 1 in the Blasted Steps, protecting pilgrims.and occasionally calming judges. (If you go into the hidden Squirrm room, he can be found singing/talking to them.) If you fight the Last Judge as your way into Act 2, he deflects the Judge's initial attack, directs the pilgrims to run, and then scars the Judge's face and leaves Hornet to finish the fight.

He has a whole bunch of other stuff he can do in the Citadel proper probably and an initially antagonistic relationship with Hornet that eventually moves to respectful. He shows signs of working himself to exhaustion protecting pilgrims/veering into becoming haunted as she talks to him more. At some point he runs into V1 who beats his ass, vampires the shit out of him and accidentally saves him from being haunted and then they start having their looney tunes stupidass fight rivalry across the whole Citadel. Probably has some interactions with Second Sentinel as well, help with some gauntlets, and the opportunity to spar with him repeatedly to unlock higher-difficulty versions of his match, same as V1.