Eldritch Altar

You raise walls into existence on flat ground you can see within range. You can shape these walls, creating a temple/altar/chamber or a similar structure. The structure must fit within a 120ft cube, but you decide its layout, appearance, decorated inside as you see fit.

The structure must have at least 1 entrance, taking the form of a door or gateway, and a space of your choice no smaller than a 5ft cube on the ground within the structure must be occupied by a reflective surface, such as a bowl of water, a mirror, or a crystal ball. The spell creates this surface, and you choose its appearance.

Any creature whose blood was used as the material component for the spell's casting can enter the structure freely. While inside the structure, the creature automatically succeeds on ability checks and saves made against illusions and gains truesight to a range of 60ft. When a creature whose blood was not used as the material component for the spell's casting attempts to enter the structure, either through its entrance or via Teleportation or extraplanar means, it takes 1d10 force damage and is teleported to an empty but harmless space on the ground up to 15ft away from the structure.

Also, you can spend 10 minutes concentrating on the reflective surface within the structure. If you do so, you cast Scyring without spending a spell slot or material components. When you cast the spell this way, the target you chose can be on any plane. If the spell succeeds, the reflective surface displays anything you can see via the spell's sensor. When the spell ends, a creature targeted by it learns the spell was being watched, but not your identity.

Once you use the reflective surface to scry, it shatters, and the structure vanishes as the spell ends. The spell ends if WIsh, Disintegrate, or similar magic targets the structure. The structure's walls have 150 hit points and are immune to poison and psychic damage.