Actually there are five things that can happen when you get a djinni
from a magic lamp:
- You get a wish
- The djinni is tame ("Thank you for freeing me!")
- The djinni is peaceful ("You freed me!")
- The djinni vanishes ("It is about time!")
- The djinni is hostile ("You disturbed me, fool!")
The probability of each outcome depends on whether the lamp is blessed
, uncursed or cursed, but even when it is blessed your chance of a wish is only 80%.
Blessed Uncursed Cursed
Wish 80% 20% 5%
Tame 5% 20% 5%
Peaceful 5% 20% 5%
Vanishes 5% 20% 5%
Hostile 5% 20% 80%
Once the djinni is released, the magic lamp becomes an oil lamp. Recharging a magic lamp does nothing. Recharging an oil lamp increases the number of turns of light left in it, but does not convert it into a magic lamp.
A magic lamp is more expensive than an oil lamp. It has a list price of 50 GP in Nethack and 1000 GP in Slash'EM. It can be used as an everlasting light source if you're prepared to do without the wish.