As soon as you enter the Crystal Tower, head straight north to enter the room in the middle. Inside, examine the mirror, select Eureka Key to unlock the portal, then examine the mirror again to enter Eureka.
Tip: if you are exhausted from fighting bosses (run out of HP/MP) and need to refill, you can go straight to B8 because it has a wellspring that can restore HP/MP and revive KO'd allies.
Bestiary Checklist:
Boss: Amon
This boss is a stronger version of Hein. He starts the battle without any weakness, but once he uses Barrier Shift, he becomes weak to one of the elements: Fire, Ice, or Thunder. You'll have to use Libra (White Mage) or Study (Scholar's ability) to check his weakness. Then go all out after you know the weakness with magic items and spells.
Chests/Items:
- C-322: Bomb Arm - B1, left side, top chest.
- C-323: Heavenly Wrath - B1, left side, bottom chest.
- C-324: Arctic Wind - B1, right side, top chest.
- C-325: Elixir - B1, right side, bottom chest.
- C-326: Bomb Arm - B2, left room.
- C-327: Ribbon (Monster) - B2, tiny hidden area.
Monsters: Ninja - C-328: Shuriken - dead-end on B3, from B2 left exit.
- C-329: Arctic Wind - B2, right room, left chest.
- C-330: Heavenly Wrath - B2, right room, middle chest.
- C-331: Phoenix Down - B2, right room, right chest.
- C-332: Elixir - B3, first split, left path.
- C-333: Shuriken - B3, second split, top path.
- C-334: Phoenix Down - B3, in front of the exit.
- I-071: Moonring Blade (Monster) - B4, in an open area.
Boss: Amon - a stronger version of Hein.
Boss: Kunoichi (Masamune)
Her main damage comes from Aeroga, which is a single-target skill. As long as you can keep up with healing and reviving, there is nothing to worry about.
Boss: General (Excalibur)
This boss can use Death, which can instantly kill one of your allies. Other than that, he doesn't deal any significant damage.
Boss: Scylla (Elder Staff)
She is stronger than the other bosses because she can use high-level magic such as Flare and Holy on a single target, dealing heavy damage and possibly KO'ing someone. Make sure to always keep your allies at full HP.
Boss: Guardian (Ragnarok)
He mainly uses Quake, which deals high AOE damage, and normal attacks. One Curaga should bring everyone back to full health.
Chests/Items:
- C-335: Phoenix Down - B5, left platform.
- I-072: Masamune (Monster) - B5, right platform.
Boss: Kunoichi - C-336: Phoenix Down - B5, near the exit.
- I-073: Excalibur (Monster) - B6, southeast platform.
Boss: General - I-074: Elder Staff (Monster) - B7, left platform.
Boss: Scylla - I-076: Ragnarok (Monster) - B7, right platform.
Boss: Guardian - C-337: Elixir - B8, bottom-left chest.
- C-338: Elixir - B8, top-left chest.
- C-339: Shuriken - B8, top-right chest.
- C-340: Shuriken - B8, bottom-right chest.
Use Teleport to leave Eureka.