Activating Guardian Mode
Once your "Guardian Gauge" becomes full it will flash and glow. You can then press "v" or click the Profession Emblem next to the Guardian Gauge to call the Guardian for a certain amount of time.
Once activated Guardians have powers that increase a players skills up to a maximum of 30 seconds. These powers allow the player to use exclusive skills. These exclusive skills are strong but the more you use the exclusive skills the faster Guardian Mode is depleted. The Guardian and exclusive skills you gain depends on your profession. As your profession level increases you will become more powerful.
Hohenheim increases the summoners magic defense and allows the usage of exclusive skills such as Acid Terror that delivers powerful melee and magic damage at the same time.