Potion of gain level

Potions of gain level will cause you to go up a level. You were expecting it to sing "Camptown Races"? If you quaff a blessed potion, you will gain HP, magic power, and one level of experience setting it at some point midway between your current level and the next level. Uncursed potions will not add experience points; if you have 20 experience points and are level 2, a blessed potion would put you at ~60XP and level 3, while an uncursed potion would put you at 40 and 3. A cursed potion does something completely different; it causes you to go one level up in the dungeon, from 3 to 2 dungeon level.