In a new TV spot for Doctor Strange in the Multiverse of Madness, The Living Tribunal can briefly be seen.

America Chavez and Defender Strange are involved in some type of explosion, as they pass by multiple glowing eyed heads of the Living Tribunal.
Who is the Living Tribunal?
The Living Tribunal is a humanoid cosmic entity, with three floating heads. The being is also a caretaker and protector of the multiverse; to prevent an imbalance of mystical forces.
Doctor Strange (2016)

There was a reference to the cosmic entity; when Mordo carried the Staff of the Living Tribunal. Mordo was training Stephen Strange and explaining about relics. The objects are embued by magic, as the magic itself is too powerful to sustain.
Loki Episode 5

There has also been a live-action appearance for the Living Tribunal (that belonged to a different timeline) in episode 5 of Loki on Disney Plus. The entity was destroyed and left in the Void.
See the TV Spot here:
Doctor Strange in the Multiverse of Madness releases in cinemas on May 6, 2022.