MAngband

So I bought a weapon of *Slay Evil* from 3, and quickly discovered it had ESP on it. I've played off and on for years now, so I knew what it was when I saw it, but I can't remember what limitations it has with regards to what it detects. I noticed that Detect Evil will detect some monsters it doesn't, but am not sure of where the line is drawn. Are there any particularly dangerous monsters (or perhaps even more relevant, uniques) that don't show up on ESP?

ESP only detects monsters that have a mind. Check the spoiler files to see which ones aren't detected: they have the EMPTY_MIND flag. Other monsters with WEIRD_MIND can be partially detected. Note that ESP has a limited radius, while Detect spells/devices can detect monsters on a whole panel.

Some particularly nasty monsters are not detected by ESP. Mainly the high golems (drolems, bone golems, bronze golems) and quylthulgs (greater rotting/demonic/draconic and master Qs). When you dive below 2000ft and you miss resist poison, be SURE to detect monsters instead of relying on ESP, because meeting an undetected drolem without resist poison is probably certain death. Concerning uniques, be careful with the elementals (Vargo, Waldern...) and the Emperor Q.