Ultimate One

This is one of White Berserker’s skills.
White Berserker receives power and support from the planet itself in order to increase her specs to be one rank higher than the enemy she is facing.
…Unfortunately due to a misunderstanding with her Master Gatou she is completely unable to use this skill.
If the location of battle is on Earth, or if her opponent is something or someone that originates from Earth, she would normally be able to activate this skill without penalty or limitation. However, on the Moon Cell there are restrictions to its duration, and it seems that there are beings there of a scale it can’t exceed.

Fate/EXTRA Material: Encyclopedia of Fate/EXTRA