Tales of Xillia, like many Tales games, revises the linear motion battle system. Chaining attacks with other characters is a key element and that’s governed by the AC (assault counter) meter. When you activate link mode allied characters connect their attacks with the character you’re controlling. Each time you strike with a standard attack or technique the AC meter drops by one.
Linked attacks are set up in such a way where the player controlled character and party members set up pincer attacks so it looks like enemies are under a constant assault. Once the AP meter runs out link mode ends, but the AC meter gradually recovers over time.
Tales of Xillia also has the series standard TP or technique point meter. Using special attacks or techniques depletes this meter. Unlike AC, technique points do not recover automatically. You’ll need to use recovery items, perhaps citrus gels, to restore TP.