Rod of Tentacles (5e Equipment)
From D&D Wiki
Rod, very rare (requires attunement)
This rod has a head of warm, rubbery tentacles, and it functions as a magic mace that grants a +1 bonus to attack and damage rolls made with it. The rod has 5 charges, and regains 1d4 + 1 expended charges daily at midnight. If the rod is reduced to 0 charges, roll d20. On a 1, the rod collapses into slime and disappears. It has these properties:
Spell. While holding the rod, you can expend one charge as an action to cast the black tentacles spell.
Tentacle Golem. You can use an action to hurl the rod to the ground, whereupon it transforms into a tentacle golem. This consumes 2 charges. It remains in this form while you can concentrate on it, up to 1 minute. If it is reduced to 0 hit points, it reverts to rod form and this property cannot be used again until the next midnight. If the tentacle beast is subject to instant death, disintegration or is otherwise annihilated, the rod is also destroyed.