Does a Shield Guardian concentrate on the stored spells it casts?

Question

The party evoker obtained the shield guardian and amulet available in the published adventure

The Curse of Strahd

and is considering storing the Greater Invisibility spell in the guardian, with instructions to cast it on the party rogue when the rogue touches the guardian.

The guardian can store spells according to the following:

Spell Storing. A spellcaster who wears the shield guardian's amulet can cause the guardian to store one spell of 4th level or lower. To do so, the wearer must cast the spell on the guardian. The spell has no effect but is stored within the guardian. When commanded to do so by the wearer or when a situation arises that was predefined by the spellcaster, the guardian casts the stored spell with any parameters set by the original caster, requiring no components.

Greater Invisibility is 4th level, and targets "you or a creature you touch", so it seems like a legitimate spell to be stored. However, it is also a Concentration spell, and I am a bit hung up on allowing the Intelligence 7 construct with no Spellcasting Ability to actively concentrate on a spell.

It certainly seems like this is allowed RAW, but there is also the phrase "the guardian casts the stored spell with any parameters set by the original caster". Could the 'any parameters' include the fact that it is a Concentration spell, and the 'set by the caster' mean that it is the caster who will be concentrating on it when the guardian casts it?

Answer 1

Yes, the Guardian concentrates.

The general rule is that concentration spells require the caster to concentrate, and there are no exceptions to this in the Shield Guardian’s description.

The fact that the Guardian has a low Intelligence score and has no general spellcasting ability doesn’t affect this — there’s no minimum ability scores for player characters to cast spells, for example. This is the same as if a low-Intelligence fighter were to cast a concentration spell from a ring of spell storing.

(In fact, the Guardian’s high Constitution score will make it quite good at concentrating. Although it is, surprisingly, not proficient with any saving throws).

“Parameters set by the caster” means any of the choices that would be made when the spell is cast — targets, modes if applicable for the spell, etc. In your example, targeting the rogue is a “parameter”. The fact that the spell requires concentration by the caster is just a property of greater invisibility, not a “parameter”.