Light Cones can be enhanced in a couple of ways, includingSuperimposingthem together.
On the character screen, select Light Cone from the list on the left-hand side.
Choose “Enhance”.

Choose “Superimpose” from the left-hand list instead.
This will be accompanied by a pop-up showing you the stats of the item you’re attempting to sacrifice.
The lock icon on this pop-up can be clicked to toggle the lock on and off.

What is Superimposing in Honkai: Star Rail?





