- Examine the Regal Pawprints on level 3, at (H-7) of Beaucedine Glacier (S) while in possession of the Umbra Bug to begin the battlefield.
- TIP: Head north from the Campaign Arbiter (level 4), there will be a hole in the ground by the cliff (H-7). The hole is visible and at the edge overlooking the Regal Pawprints.
- Buffs wear upon entry. Time limit is 30 minutes, and experience is not lost upon death. Alter egos may be summoned once inside.
- You will fight alongside Lilisette. You have approximately 2 minutes, 30 seconds to prepare before Lilisette will engage Cait Sith Ceithir on her own.
- Cait Sith Ceithir will primarily use AoE or single-target black magic, and some enfeebling white magic spells.
- Regal Scratch: Single-target damage.
- Divine Favor: Removes all of Cait Sith Ceithir's status ailments. Possibly will not use this ability unless there are ailments to be removed.
- Mewing Lullaby: AoE sleep and TP reset to 0.
- Eerie Eye: Gaze Amnesia and Silence with a range of approximately 20'.
- Level ? Holy: 25' AoE light damage centered around its target.
- Cait Sith Ceithir will occasionally summon Atomos, who will use the following abilities in order before disappearing:
- Soul Vacuum: Reduces all attributes by points from Lilisette and all party members within 25' of her.
- Soul Infusion: Bestows all drained stats from Soul Vacuum to Cait Sith Ceithir, temporarily increasing his power drastically.
- These effects last approximately 1 minute and cannot be removed until they wear.
- After defeating Cait Sith Ceithir you will get a cutscene.
- If you fail, you will have to get a new Umbra Bug from the Regal Pawprints at the southern Pso'Xja tower at (H-10). You may only obtain an Umbra Bug once per Vana'diel day.