There are two types of Combat in Atlantica Online: Standard/Normal Combat and TBS
Tactical Battle System (TBS)
The Tactical Battle System is a more freely moving type of combat that is used for TBS missions, was well as some quests.
Some monsters scale their level to the level of the highest Main Character in a Party when Combat begins. This can be good (Experience is based on the highest level character in the fight) and bad (Damage is based on the highest level character in the fight).