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?