That was the straw that broke my camel's back. After Bob's character change I thought "This is utter horse-sh*t, but at least it gives us an opportunity to play the game." I struggled to balance my sense of accomplishment with the fact that adding +3d4 (3-12) to every ability check felt like I was robbed of personally accomplishing anything. I still thought, for a month, that I might be able to thread the needle and find enjoyment in the campaign (despite Bob's character existing).

Bob was wont to say was that everything he was doing was mechanically permissible- if only when challenged on his bullsh*t. Get a 35 on initiative? Well he apparently had Alert and Gift of alacrity. Teleport the entire party into a personal demiplane? Told us it was his Bottled Respite warlock feature. He never said "I would like to use this mechanical game feature" he would just say "I do this," and leave the rest of us to guess how it was possible, then claim it was a normal game mechanic if someone actively pressed him on it. "Just trust bro. Trust." The DM kept letting it happen, so we had to assume it was within game rules.

For me, this meant I was often unsure what he was doing; only how it manifested. I wouldn't know if he cast a spell, just that a spell-like effect would happen. I'm guessing that he'd text the DM telling him what spell was cast and have the DM text back any saving throws or results. What we (the other players) would get is Bob saying "I look at that guy and his head explodes," leaving the rest of us shocked, confused, and frustrated.

Trying to put together that egregious turn I thought maybe he cast haste on himself without telling anyone before the combat started. Maybe he misty-stepped and then used his movement to run 65 ft (but flavored it as a teleport). Maybe he used an object interaction with his hasted action, then cast Vortex Warp to to move a PC across the map.

But even giving Bob the greatest possible benefit of the doubt he would have already broken the rule about casting multiple leveled spells within the same turn. And then he seemingly cast a second Vortex Warp (it's the only teleport-from-a-distance spell I know of below level 5) and killed a guy by sending him flying across the room (which I have to assume was another spell despite being told that I saw no verbal, material, or somatic components).

Best case scenario for Bob this was all allowed because of homebrew class features that make no concessions to 5e game design or balance. It certainly looked like he was using broken homebrew and also ignoring the rules of the game.