# Portal detection methods

A user has suggested this page be merged with "Trap#Detection"

There are several ways to detect portals.  Portals count as a trap and can be found any way that a trap could be.  This is most important on the Elemental Planes, where finding the portals quickly is important.  The usual methods are:

Read a blessed or uncursed scroll of gold detection while confused. This will find and display all traps on the screen as if you had seen them.
Read a cursed scroll of gold detection. This will show a pile of gold at every trap location. It should also be noted that the gold will disappear when you come within line-of-sight of it, making it fine on the Plane of Earth and Plane of Air if you can memorize the location it was at, but not terribly useful on the Plane of Water, where the portal moves, nor on the Plane of Fire, where there are many fire traps and moving light sources (you'll see gold on the traps and on the portal until the gold becomes visible).
Use a crystal ball and choose to search for ^. Note that this will leave you immobile for d10 turns, which can be dangerous if you're low on HP or are being attacked, and has a chance of failing if your intelligence is less than 20.[1] Because of the paralyzing effect, it's not a preferred method to detect the portals on the Planes, but it's workable if you have no scrolls of gold detection or are going for the illiterate conduct. (Getting engulfed by a vortex before attempting to use a crystal ball on the Plane of Air or Plane of Fire is a wise move--if you're engulfed by an air elemental while helpless, you may lose a lot of HP.)
Zap a wand of secret door detection or the detect unseen spell, which will detect the portal (and all other hidden traps and doors) if it is within radius of 8.
Apply a charged Bell of Opening -- this will work the same way as the wand of secret door detection.
Wield or wear the Amulet of Yendor -- this works only on the Planes, and only detects portals, not traps. There is a 1/15 chance each turn that you will get messages ("The Amulet of Yendor feels warm.") if within 12 squares of the portal.[2] See the Amulet of Yendor article for more details.
References

↑ src/detect.c in NetHack 3.4.3, line 864

↑ src/wizard.c in NetHack 3.4.3, line 65

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