Complex sentence: The biggest change to the battle system and also counting as a brand new feature is the "Tactical Link System", which allow players to follow up with three different kinds of link attacks, dealing additional damage and providing various other benefits.
Split into simpler sentences: The biggest change to the battle system and also counting as a brand new feature is the "Tactical Link System". The "Tactical Link" allow players follow up with three different kinds of link attacks, dealing additional damage and providing various other benefits.