The 13th battalion was a clone legion that served under Jaro Tapal and were present during the great Jedi purge. Their armour is white with yellow markings.
The first sighting of the 13th battalion is on Zeffo where in the water along with normal phase 2 clone troopers is one 13th battalion member.
Their second appearance is a flashback on Dathomir in which Cal Kestis is a Padawan when the commander gets the word and attempts to kill Jaro Tapal. he fails this results in the alarm going off and Jaro Tapal killing multiple squads a battalion of clones shot Jaro Tapal while the others continued to shoot.This is the last time they are encountered in the story.