Do you lose or keep your experience when you lose levels?

Question

I was playing 1st Edition D&D not long ago. We had a case where our ranger broke a door down and charged into a room with two wraiths that sucked both his levels out of him, which killed him.

I didn't ask at the time what would have happened if he was on level 3 rather than 2 when this happened, but I've wondered.

However, I've moved on to D&D 5e since then, so I'm not interested in the AD&D rules for this anymore, just the 5e rules for it. In 5e, would his experience total remain the same after losing two levels (from 3rd to 1st)? If not, would he level up as normal and if so, how would he level up from that point on?

Answer 1

There are no monsters or effects in 5e which drain levels/cause loss of experience.

Most of the monsters we'd have once associated with XP drain now have attacks which will drop one's maximum HP. These include the demilich, specter, *cubus, wight, and wraith. A shadow has an attack which drops one's strength score.

Even the Deck of Many Things, one of the game-break-iest things in D&D, won't cause one to lose a level. The Fool, when drawn, will cost 10,000 XP. But "if losing that much XP would cause you to lose a level, you instead lose an amount that leaves you with just enough XP to keep your level." That is, you may lose only one XP if you'd just crossed a level-threshold. (DMG p.164, with thanks to @xanderh for the pointer.)

If you chose to incorporate level/XP loss, you're into homebrew territory.