Ant Lion
The Ant Lion is the first monster you face after departing from the Will-o-Wisp Academy. It ambushes you on Erd after using Lassi's Wild Wind Magic to calm a raging sandstorm and allow you to continue. Some consider it to be the first boss you have to face, but it could generally agreed upon as a mini-boss instead.
It has two known attacks, Tail Swipe and Sand Blast. Tail Swipe focuses on one character while Sand Blast hits both characters.
Overall, the Ant Lion is an Earth Starsign, and is weak against Lassi's Wind Talon.
Expect a level-up from both characters after this battle.