Lotus Reverie: First Nexus

-- If the human host dies, the tulpa will also die, and vice versa. For this very reason they are forced to cooperate with each other if they want to stay alive.

-- The only way to extend their lifespans is by fighting and killing another Tulpa and their host in a duel. This is the only moment where a Tulpa loses their immortality and becomes vulnerable.

The second great change came with a huge monolith that towers up as far as the eye can see standing where the royal palace was supposed to be. This monolith has inscribed six rules making clear only one thing:
From among all the remaining people in Maya, only one human and their Tulpa can survive.

[From Keinart Lobre]