From the publisher:

Master of Tactics

Finally, you may stand beside Ardus Ix’Erebus, a member of Waiqar’s first and greatest legion, the Deathborn Legion. Ardus has lived for centuries and fought in countless battles, giving him unparalleled first-hand knowledge and understanding of tactics. With the help of this undead commander and his First Legion Plot deck, even the lowliest monster fights beyond your expectations.

The First Legion Plot deck invites you to use Ardus Ix’Erebus’s battlefield knowledge to your advantage. You can increase your monsters’ attacks, reward them for fighting in formation, or inspire them all minion monsters to use the abilities of a master monster with Rise to the Challenge. Although these lesser creatures may never attain to the level of Waiqar’s Deathborn Legion, the leadership of Ardus Ix’Erebus certainly makes a difference.

Just as Ardus Ix’Erebus has had centuries to perfect his battlefield tactics, he’s had immeasurable experience engaging in combat personally, making him one of the most dangerous warriors in Terrinoth. When Ardus joins you as your agent in another campaign, you may flank your opponents with other monsters, cut through their defenses with a forceful blow, or rally your warriors around you to make a single devastating push. Whether Ardus Ix’Erebus fights on the front lines or commands from afar, he’s undoubtedly one of the greatest assets available to you.