dnd 5e – Dnd 5e Ruling on auras while in Imprisonment

Ok, Little Help needed.

Hollyphant
Aura of Invulnerability.An invisible aura forms a 10-foot-radius sphere around the hollyphant for as long as it lives. Any spell of 5th level or lower cast from outside the barrier can’t affect creatures or objects within it, even if the spell is cast using a higher level spell slot. Such a spell can target creatures and objects within the barrier, but the spell has no effect on them. Similarly, the area within the barrier is excluded from the areas affected by such spells. The hollyphant can use an action to suppress this trait until its concentration ends (as if concentrating on a spell).

Sequester
If the target is a creature, it falls into a state of suspended animation. Time ceases to flow for it, and it doesn’t grow older.

Imprisonment
Minimus Containment. The target shrinks to a height of 1 inch and is imprisoned inside a gemstone or similar object. Light can pass through the gemstone normally (allowing the target to see out and other creatures to see in), but nothing else can pass through, even by means of teleportation or planar travel. The gemstone can’t be cut or broken while the spell remains in effect.

Basiclly I want a hollyphant in a gem necklace, so i be immune to spells of 5th level and lower.

Does this RAW/RAI legally work?