(Note: this is useful for a DM wanting to do a homebrew world or campaign or who is struggling)

Not a magic item, but both a gift and a curse.

Acquisition: "You gazed into the void, and the void gazed back." Somewhere in your past (backstory) you were either in the void of limbo or somehow gazed into it, had a vision of it, or communicated with something in it. In doing so, a chaotic being known as Tempafera (the Time Beast, more on him at end of description) bestowed upon you his mark in the hopes that you will loose chaos on the physical plain and become the monster that he wishes you to be. Will you rise above his evil desires, or will you fall to them? The choice is yours.

Physical Description: The Wrath of the Void appears as a medium/large darkly colored crack-like mark visible somewhere on your body. If clothing or gear would obscure the mark, a holographic image of the mark appears affixed to the surface of what is covering it.

What does it do?

As an action, you may touch the mark and will it to activate. Upon doing so, you transform into your void beast (see my homebrew creations to find the different void beast options; your void beast is the beast which you first transformed into when given the Wrath of the Void in your backstory) until you take an action to transform back. Your hit points becomes your void beast's hit points plus half of your hit points rounded up that you had before transforming as temporary hit points on top of that. Weather or not armor or weapons or gear stays on you, is dropped, or is transformed with you is stipulated in your void beast's description. The Wrath of the Void also changes some of your character's traits and ability scores depending on your void beast (see void beast descriptions in my homebrew creations for specifications.

Also: as time seems to work differently with you (being marked by a time god) you cannot sleep nor fall unconscious nor be charmed, and you need no sleep. (A long rest consists of you sitting quietly and motionless, observant and with your thoughts. Also, you no longer age and cannot grow tired or exhausted (except for magical exhaustion).

About Tempafera: He is an ancient genius-loci-god who appears as either a giant moon-sized eyeball, a writhing mass of tentacles and random beast-like faces, or a giant man with two heads and four arms with a huge clock bound in giant chains around his neck. Long ago, the gods imprisoned him in limbo due to his chaotic ways. He has created countless horrific monstrosities and creatures, and found ways of loosing them from time to time back into the world. While he is bound to his own floating labyrinth in limbo, there is a very small entrance through which he can just barely interact with and influence the physical world. His labyrinth is constantly changing, and full of traps, monsters, magic, trapped adventurers, void beasts locked in their beast form, and lots and lots of treasure. He enjoys trapping people or luring them into his realm to see how they fair until he grows tired of them and sends them back, and one historical account speaks of a gladiator style fight pit in the middle of his labyrinth.

Note: I am sorry for the long description. More void beasts will be being made soon. DMs please use this, and players please discuss this with your DM. In my homebrew I will also post a few character sheets using this to show examples of how this would look in game.

Notes: Automatic attunement upon infliction in backstory (see description), non removable, can only have one., Social, Shapechanging, Cursed, transmutation, enchantment