This ring seems rather unremarkable, other than the tiny doorway that has been etched in one of it sides. While attuned to the ring of storage, you may use an action to stretch the ring into a 5ft wide by 10ft high doorway. This dooway leads to an interdimensional space unique to the creature it is attuned to, 30ft by 30ft in size. This space remains in existance for one minute, after which the doorway closes, returning to its ring form. All creatures are ejected from the space when the doorway closes. Objects that are placed within the space stay in their position. Time passes as usual within the space the ring creates.

While wearing the ring, the finger that its on is within the space, making it appear as if the finger ends at the ring. Whenever the attunement ends all the items appear in the place the doorway was last opened. 

Placing a ring of secret storage inside an extradimensional space created by a handy haversack, portable hole, or similar item instantly destroys both items and opens a gate to the Astral Plane. The gate originates where the one item was placed inside the other. Any creature within 10 feet of the gate is sucked through it to a random location on the Astral Plane. The gate then closes. The gate is one-way only and can't be reopened.

Notes: Utility, Container