Voadam said:That's a plot device for why you can play your old character in a 1st level game. "And so though I destroyed the Tome of Xiphid, it cost me all my magical power. I've had to start all over."
A plot device I've actually used back in 2nd ed.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.