A full genre switch to tower defense. Instead of piloting a ship, you defend a core crystal by deploying heroes that auto-fight waves of monsters marching toward you, each stage on a 180-second timer.
A deep sub-game: 99 stages (27 boss stages), 52 deployable heroes across 9 types, a separate 75-level Fortress XP track, battle buffs, and random events. The core you protect is the "Wish Crystal". Sample of the hero roster: