Simple solution is “resistant damage” - damage taken by burning your life force to power spells can only be healed by natural healing, not magical healing. It’s tracked separately, and similar to subdual damage, you add it together with normal damage to determine if the character reaches 0HP. If you choose to go this route, I suggest that HP not be your primary fuel for spellcasting, but rather have the patron grant a class feature that allows “overcasting” by burning one’s life force to power additional spells after you’ve run out of normal spell slots.
Funny thing is, a real life Metaverse has existed for over 20 years. The term Metaverse comes from a book called Snow Crash. The game Second Life was designed explicitly to be the Metaverse envisioned in Snow Crash, complete with it’s own economy tied to real life money (as in, if you made enough money in-game, you could cash it out for real-world USD). Companies used to build headquarters in the game world similar to how some do in Fortnite now, even going so far as to hold actual real world business meetings in-game as a form of teleconferencing. After a few high-profile events where live TV broadcasts of in-game events got swarmed by flying dicks, the media lost interest in the game, and companies abandoned the game and moved on to more business-oriented solutions.