Role-playing Games Stack Exchange is a question and answer site for gamemasters and players of tabletop, paper-and-pencil role-playing games. It only takes a minute to sign up.
Sign up to join this community
An Unseen Servant has an AC of 10 and 1 hit point, which means that it can be targeted by actions and effects that use attack rolls, and that it can be destroyed by taking damage.
However, the spell text doesn't have any information about its saving throws. What happens if it is targeted by a area spell or effect that requires a saving throw, such as Fireball?
This spell creates an invisible, mindless, shapeless force that performs simple tasks at your command until the spell ends.
The presence of an AC and HP value does not make it a creature, even objects (such as Bigby's Hand, Barrels, and Walls) have AC and HP (and a strength score, in the case of Bigby's Hand). As for the Servant having a Strength score, I suspect it's for determining how much it can lift, drag or carry.
Because the Unseen Servant isn't a creature, most spells that can target a single creature (if the caster can see invisibility), can't legally target it, neither can Area of Effect spells that hits creatures, such as Hypnotic Pattern, affect it.
It can, however, take damage from Area spells that deal at least 1 damage- then it is destroyed.
An unseen servant is an object. It automatically fails it's save.
Justification
There are only three classes of target in the D&D rules: creatures, objects and locations.
AN unseen servant is a target; otherwise its AC and HP would not have been specified.
From the Making an Attack section:
- Choose a target. Pick a target within your attack’s range: a creature, an object, or a location.
From the Casting a Spell section:
A spell’s description tells you whether the spell targets creatures, objects, or a point of origin for an area of effect (described below).
An unseen servant is not a creature (it is mindless). It is not a location (it moves around). Therefore it is an object.
Objects always fail Strength and Dexterity saving throws, and they are immune to effects that require other saves.
If the unseen servant is in the area of effect of a fireball then it fails its save and is destroyed (since fireball always does more than 1 HP damage).
Additionally, an unseen servant is invisible so cannot be targeted by any feature that specifies "that you can see". If you attack it, you roll at disadvantage because you can't see it - but you can still attempt the attack. If you hit AC 10 and do at least 1 HP of damage then it is destroyed.
