Yux

Yux are X-shaped, barrier-using creatures created by the X-Naut army, appearing in Paper Mario: The Thousand-Year Door.

Paper Mario: The Thousand-Year Door
They are first encountered in the Great Tree where they are used as security by the X-Nauts. A smaller number appear later in the X-Naut Fortress on the moon, where they can be seen behind glass alongside the stronger Z-Yuxes and X-Yuxes, which are used as guards there.

In battle, Yux produce a Mini-Yux from within themselves at the end of every turn; the Mini-Yux sustains a barrier around the Yux that renders it invincible. The Yux attack with ring beam that pierces defense; even Damage Dodge badges have no effect on the damage they deal. This means that a Yux's attack will always deal at least one damage unless the target performs a successful Superguard.

During the battle against Sir Grodus, he uses a type of Yux called Grodus X, which acts more like a Mini-Yux.

Super Paper Mario
In Super Paper Mario, normal Yux do not appear, though similar enemy called a Barribad appears alongside a few of its own variations. Additionally, one of the Sammer Guy warriors of Sammer's Kingdom is named Yowling Yux in tribute to the enemy.

Names in other languages
Crucimat Rostella