Hidden

Creatures that are hidden are invisible to other creatures. They cannot be interacted with, but can still be struck at if the player force attacks in that direction.

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Reason: Can non-player creatures search? Does Clairvoyance reveal lurkers within its AOE?

When a player character walks past a hidden creature, they search all adjacent tiles. A random number is rolled from 1 to the searcher's Intelligence, plus any additional bonuses to searching they may have. If this is greater than the hidden creature's difficulty, they will be revealed. This search can be performed multiple times by stepping back and forth until the hidden creature is revealed. True Kin characters can install a Penetrating radar implant to unerringly reveal any lurkers within its AOE.

List of Hidden Creatures

Creature	Difficulty
elder lagroot	Hidden at 23
holographic beth	Hidden at 18
holographic ivory	Hidden at 15
lagroot	Hidden at 20
lurking beth	Hidden at 18
sprouting orb	Hidden at 16
yonderbrush	Hidden at 15
young ivory	Hidden at 15

On sewage eels

Sewage eels behave slightly different from other lurkers. Rather than existing but in hidden state, eels initially are nothing but a spawner, due to which they cannot be attacked until successfully revealed. Also their search difficulty is not a check against static number, but a percentage chance derived from searcher's Intelligence stat (look at eel's page for exact formula).