Drain resistance prevents the following attacks:
- The drain life monster attack. All V vampires and W wraiths have this attack, as does & Demogorgon. If the compile-time option SEDUCE is not enabled, & foocubi become level-draining monsters as well.
- The drain life ability of The Staff of Aesculapius and Stormbringer.
- Directing the spell of drain life at oneself or a monster.
- Being seduced by a & foocubus and getting a negative effect, with the compile time option SEDUCE enabled (the default). This is one of five possible negative effects.
- Suffering a god's anger through incorrect prayer or sacrifice. This is one of many possible effects.
- In SLASH'EM, being zapped by a wand of draining.
Acquiring drain resistance
Drain resistance may be acquired by:
- Wielding Stormbringer, Excalibur or the Staff of Aesculapius grants extrinsic drain resistance.
- Polymorphing into a monster with drain resistance.
In SLASH'EM, drain resistance can also be acquired by:
- Wearing deep dragon scales or deep dragon scale mail.
- Wearing an amulet of drain resistance.
- Wielding the Hand of Vecna
- Starting the game as a lycanthrope or vampire.
- Being an undead slayer or necromancer.
Monsters with drain resistance
Drain resistance is intrinsic in:
In SLASH'EM, the following monsters are drain resistant in addition the above:
- adult deep dragons (but not babies, strangely enough)
- undead slayer player monsters
- All the new undead, lycanthropes and demons
Drain resistance usually acts silently. Only the lack of level drain messages indicates it is operating.
When consorting with a foocubus, the message "You have a curious feeling" indicates that you would have lost a level, but the loss was prevented by drain resistance.
In vanilla NetHack, drain resistance is not especially important; this is because monsters' level drain attacks are subject to magic cancellation. By the time such monsters are encountered, most players will have a magic cancellation of 3 and a successful drain life attack will be extremely rare. Even then, a single point of experience is enough to regain the occasionally drained level.