Overdrive Mode aka Overdrive is a new skill type introduced with the Stormcaller Update patch on October 24, 2013. Overdrive is a set of skills (well, just 1 for now) that all players can use, regardless of main character class, and it is well worth having!

Overdrive mode includes a gauge located at the bottom of the screen, and fills after defeating enemies. Once this gauge is full, the skill, Ancient Fury can be activated. The gauge can be increased by attacking enemies, as well as, by casting magic.

Attacking enemies lower in level will not increase the gauge.

You can obtain the Overdrive skill quest at level 60 from NPC Master Simon in Rome's Plaza. You can find this quest in the Quest Log under Sub Quest > General.

List of Overdrive Skills: