Natural Invisibility

A Monster Trait.
From the Book of Engoku:

Description

This creature’s natural state is completely see-through. While unseen, the creature cannot be attacked or targeted for spells unless something is used (at the Reeve’s discression) to outline the form of the creature, or the creature takes offensive action. The creature must keep its arms crossed to denote invisibility. The creature can become visible and invisible at will, simply by crossing and uncrossing its arms. Becoming invisible is subject to ‘shot in motion’ rules.

See-through creatures

• Nurikabe