Ouroboros

Ouroboros are entities in Xenoblade Chronicles 3. They are s who can take the form of giant, vaguely-humanoid entities with a purple or white hue, depending on the nation. Two characters with an Interlink may temporarily combine to take on an Ouroboros form.

Description
While in Ouroboros form, the two individuals Interlinked share the body of a single giant humanoid. They can also see each other's memories. However there are limits, the Interlink overheats and beeps and if they stay in that form for too long, an annihilation event will occur that will likely kill them. Limbs of an Ouroboros can be severed and grow back, but at the cost of energy consumption, causing the Ouroboros form to overheat faster.

As a gameplay element
Each of the three interlink pairs among the main playable characters ( &, & ,  & ) may (independently) combine into Ouroboros form during combat. This changes the moveset made available to them.

The form of the Ouroboros taken, as well as the moves made available as a result, depends upon which member of the pair takes the lead. This may be swapped at will; for example, if Noah and Mio are currently in Ouroboros form, the form and moveset may be swapped between that of Noah's Ouroboros and that of Mio's Ouroboros.

Trivia

 * Ouroboros forms are very similar to the Gears in Xenogears.
 * Noah's Ouroboros form is similar to Weltall.
 * Sena's Ouroboros form is similar to Crescens
 * The name 'Ouroboros' is a reference to the symbol of the same name: a dragon or snake eating its own tail, commonly interpreted as representing eternal cycles. This symbol is also seen in Xenoblade Chronicles 3.