Questions from this page use the current page as the primary answer context.
Description
The Hiding skill allows players to become invisible to other players and most creatures. The player will remain hidden until performing a 'revealing' action such as spellcasting or usage of certain skills or items. Players with the Stealth skill, however, can walk and remain hidden. Players can potentially be revealed by other players with the 'Reveal' spell or through the Detect Hidden skill. When hidden and making a weapon attack against a creature, if the player has 80 skill or more in both Hiding and Stealth, they can perform a 'Backstab' attack for vastly increased damage.
Summary
Allows the player to become invisible indefinitely
You must be a good distance away/out of sight from any mob (creature or player) for this to succeed. However, one thing you can do is turn around a corner and immediately hide since you are out of sight.
You can not raise this skill (or detect hidden) while in a house you are at least friended to, as it will always work there
Chance to hide is equivalent to the skill level (50 skill = 50%, etc)
Players who are Friended to a house receive an effective bonus of 100 Hiding skill for making Hiding attempts inside that house (non-Friends no longer receive any bonuses, will not gain skill)
All players who are within 1 tile of a house, but not actually inside in that house, will receive an effective bonus of 50 Hiding Skill for making Hiding attempts
Required by the Stealth skill to make movements while hidden
Can be paired with the Stealth skill to make Backstab attacks against creatures
Players who are revealed via Detecting Hidden or the Reveal Spell cannot become Hidden or Invisible by any means for 5 seconds
Players who are revealed also cannot Eject from a house for 5 seconds
Hidden players that are Revealed due to a creature ability will be prevented from any form of Hiding/Invisibility for the next 10 seconds
some higher level creatures may have longer durations
Training
Note: Players cannot train hiding in places where they have effective hiding bonuses, i.e. friendly houses/inn rooms.