A summon is a creature that was magically drawn from another plane of existence, or simply from the nearby environment. A summon is compelled to do the bidding of the one who summoned it. Most summons have a time limit, after which the creature is returned to the place from which it came (it is unsummoned). In addition, a creature can be manually unsummoned at any time (by selecting the "Unsummon" option in the creature's radial menu). A summoned creature is also unsummoned when its summoner dies.

Neverwinter Nights limits characters to a single summon at a time (although certain scripting tricks can get around this); if an additional creature is summoned, the previous summon is unsummoned. This summoned creature counts towards the party size penalty, so it will reduce experience awards for kills. Killing a summoned creature does not grant experience points.

The school of conjuration is responsible for all spells which are able to summon a creature or object. These spells leave an effect on the summoner, which means that a creature could be unsummoned if the summoner is dispelled. This effect has the side-effect of blocking horse riding for the summoner (until the duration expires or the summoner rests).

The paladin's summon mount feat, while having "summon" in its name, is technically not a summoning. A paladin's warhorse is not subject to the "one summons" limit, nor does it have an "unsummon" option in its radial menu. (To unsummon a paladin's warhorse, it needs to be assigned to itself using the "assign mount" option in the horse menu.)

Custom content notes

• Summoned creatures are not shown in the Toolset palette, as they are not normally directly part of a module. An override that makes them visible is available on the Vault.
• When creating a custom summoned creature, the creature's event handlers should be set to the "nw_ch_ac*" set (or some custom equivalent), with the option of instead using nw_ch_summon_9 for the OnSpawn event. (The difference between nw_ch_ac9 and nw_ch_summon_9 is that the former has extra overhead for placed horses, while the latter supports the incorporeal flag.)