In the DMG, the Bag of Holding, Heward's Handy Haversack, and Portable Hole all contain the same language indicating that placing any one inside another (naming those three items by name "or similar item") creates a temporary gate to the Astral Plane, sucking all creatures within 10 feet there.
The Quiver of Ehlonna, like the other three, contains extradimensional spaces, but does not contain this paragraph. Does it work for creating one of these temporary gates?
Best Answer
It will open a gate.
The key language is "similar."
The referenced description states:
The first three items, the Bag of Holding, Heward's Haversack, and the Portable Hole are all variations on a theme. So the question is if the Quiver is similar to them:
Considering that even the haversack, the hole and the bag have some differences I would rule that the quiver has enough similarities to be considered similar to these three items, and especially so because it is described as using extradimensional space. Hence, placing the Quiver in any of the others would open a gate to the Astral Plane.
Left unsaid is what happens if the quiver is ruptured. The bag and the haversack each have different consequences for being ruptured while the hole and the quiver make no mention of it.