JP Boss Guide by /u/Zurai001

Multiplayer Enemy AI by /u/TFMurphy

BOSS: Seymour Natus (X)

Difficulties: 160 (Ultimate ) and 220 (Apocalypse )

Mastery Conditions:

• Win with 4 or more party members alive.
• Reduce Seymour Natus' RES.
• Reduce Seymour Natus' MAG.

Overview:

• Two targetable enemies in this fight - Seymour Natus himself, and his companion Mortibody.
• Seymour Natus' main arsenal includes NAT Chain -ra spells (Fire/Ice/Lightning/Water), Ultimate: Break (low chance to Petrify up to 3 random party members), and Ultimate: Flare (piercing heavy non-elemental magical damage, high chance to Sap).
• Seymour Natus counters PHY attacks with Counter Protect, and BLK with Counter Ultimate: Flare. It starts out at 10% counter chance, but increases to 20% from Weak phase onwards.
• Mortibody has AoE -ga spells, which deal massive Fire/Ice/Lightning/Water magic damage respectively. But notably, it has a powerful attack called Ultimate: Desperado which deals massive AoE physical damage, and comes with Ultimate: Dispel.
• Mortibody cannot be killed, and if its HP were to be dropped to 0, it will use Mortisorption to absorb some of Seymour's HP to sustain itself.
• Mortibody is vulnerable to Stop.
• Both Seymour and Mortibody are weak to Holy (Seymour being slightly weak). Seymour resists Thunder, Earth, Wind and Dark.

Tips:

• Bring Stop to stop-lock Mortibody. Important.
• It doesn't say in Zurai's guide that he is vulnerable to Reflect. You can possibly go full on physical, Reflecting him so that Counter Protect is a null mechanic. You might want to wait for TFMurphy's AI update to confirm this. Alternatively, just bring someone like Ramza/Gilgamesh who have in-built Banishing Strike commands in their BSB (with Ramza being a little bit more useful since it's Holy-elemental, but party DEF 100% vs. Sentinel isn't much difference anyway, as this fight is heavily NAT magic based).
• Other than that, you might want to gear for Petrify resistance as it's the one status that could screw up your run. Soft Bracer (X) is an accessory that provides such a resistance.
• Debuffs will also be amazing here. Hi Vaan.