Transcendence

You ascend and create reality using your own body and mind as the source. To cast, you must lie unconscious on the stone tablet, covered in your own blood for 7 days. The bed will then crack and you will have successfully cast the spell. If you are woken during the period of casting, you your blood starts to boil, burning you from the inside and out, killing you without any death saving throws.

Once cast, your conscience gets transported to the Abyss, where it can take any form you’d like.

Your body maintains itself as though it were still alive, although it no longer breathes. It now acts as the carrier of a new plane of existence, which you may create. Your body may grow features that resemble the plane you’ve created.

You may designate items to enter into the plane of existence you’ve created. To do so, you must spend 8 consecutive hours concentrating on an item that you can see without any interruptions. There is no limit to the number of items you can transport into the new plane, but note that (with DM discretion) some items may be so large or so powerful that transporting them may simply kill you in the process. You are not limited to inanimate objects, and may also transport a living creature. An unwilling creature must also save on a DC 20 Wisdom saving throw for the spell to work on them.

You may also create any number of magic items for your plane of existence. These items are fuelled by your conscience from the Abyss, in the same way a Cleric’s magic is fuelled by their deity. Any items created this way will lose any features if they are to leave the plane in any way.

You may also create creatures that exist only in your plane of existence. If you do, they do not have their own consciousness but rather occupy a portion of your own. They die instantly if they leave your plane and if they die in any way it also kills part of your conscience. Killing your conscience also instantly kills any creature created this way.

Teleportation spells that can transport to different planes of existence, as well as the wish spell, have no effect when trying to leave or enter this plane.

The dream spell may work on you once this spell has taken place. You are treated as asleep in this case and the user may influence your plane of existence in a limited way (at the DM’s discretion) when casting the spell.

A creature that exists within your plane of existence can escape by killing every created creature. Once the last creature has fallen, it drops what resembled a heart that resembles your plane is some way. A creature can touch this heart and it will create a portal for 10 minutes. Once closed, there is no other way that another creature can leave. 

A creature can destroy this plane of existence, along side any living creature inside it, by puncturing the skin of your body with a weapon you designate before casting this spell. Your conscience is not killed by this process, but is rather permanently trapped in the Abyss for the rest of time, cannot escape by any means (magical or non-magical), and has no ties to any other plane of existence.