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?