A extinct volcano is excavated and webbed with octarine filigree.  Can store up to 100,000 resources without degradation and immune to magic, when powered by a Stasis spell.

The cavern is a physical building on the planet.  The contents are physically located on that planet.  As the planet goes so goes your stuff.

Stasis is basically Create Force Field, but on your cavern.  No 12 week buildup.  Lasts 10 weeks.
The resources are stored in the caverns, but the protective effects are reliant on the spell.
Protected resources cannot be recovered during the spell's effect.
One cavern per planet.