Rod of Elemental Stasis

This wooden rod is set with four glass spheres that each contain a microcosm of elemental energy. If an air elemental, a fire elemental, an earth elemental, or a water elemental is slain within 60 feet of you while you are holding the rod, the elemental is absorbed into the rod. A creature absorbed in this way occupies one of the four crystals in the rod. If the four crystals are already full when an elemental dies within range, the elemental dies as normal. As an action, you can present the rod and free one of the elementals contained within a crystal. The freed elemental appears within 5 feet of you and is friendly to you and your allies. Roll initiative for the summoned elemental, which has its own turns. The elemental obeys any verbal commands that you issue to them (no action required by you). If you don't issue any commands to them, they defend themselves from hostile creatures but otherwise take no actions.

A freed elemental remains for 10 minutes, until you dismiss it, or until it is slain, after which it disappears to its home plane.

Arcane Focus: An arcane focus is a special item designed to channel the power of arcane spells. A sorcerer, warlock, or wizard can use such an item as a spellcasting focus.