Armored Core 6 Ibis Series CEL 240 boss guide: Best build, weapons, OS tuning, and more

The Ibis Series CEL 240 is arguably one of the toughest boss you will encounter on your first playthrough of Armored Core 6 Fires of Rubicon. FromSoftware are well-known for their challenging, but fair boss designs. From Dark Souls 3's Nameless King to Elden Ring's infamous rot goddess, Malenia, FromSoftware has been the architect behind some of gaming's toughest bosses.

And their latest mech-action title, Armored Core 6, seems to continue this tradition with bosses like Balteus, Sea Spider, Ayre, and more. The Ibis Series in particular is where I feel most players, especially newcomers, will face a lot of trouble, after Balteus or the Sea Spider.

Not only does the boss have some really powerful attacks at its disposal, but it is also the very first boss in the game to have two phases. Fortunately, much like any other boss in Armored Core 6, you can get an upper hand in the battle against Ibis Series with the right build and weapon loadout.

Here's a comprehensive guide on how to easily defeat the Ibis Series CEL 240 in Armored Core 6 Fires of Rubicon.

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Best build to use against the Ibis Series CEL 240 in Armored Core 6 Fires of Rubicon

Not only does the Ibis Series use Reverse Joint legs giving it unparalleled midair maneuverability, but it also has access to melee weapons like the Coral Oscillator - Redshift, which can be used to easily stagger your AC, while also dealing direct damage.

Here's a build I used on my first playthrough, that helped me easily defeat the Ibis Seires CEL 240 in Armored Core 6 Fires of Rubicon:

• Right-arm unit: Vvc-760PR
• Left-arm unit: SG-027 ZIMMERMAN
• Right-back unit: VE-60SNA
• Left-back unit: VP-60LCS
• Head: EL-TH-10 FIRMEZA
• Core: EL-TC-10 FIRMEZA
• Arms: EL-TA-10 FIRMEZA
• Legs: EL-TL-11 FORTALEZA
• Booster: (Nothing)
• FCS: VE-21B
• Generator: VP-20D
• OST Expansion: Pulse Protection

The Ibis Series CEL 240 is quite weak against plasma damage, and much like Balteus and Ayre, can be easily staggered with high-impact plasma weapons. The rail-gun and plasma cannon combo is something that I found to be very effective against some of the toughest late-game bosses in Armored Core 6.

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Tips to easily defeat the Ibis Series CEL 240 in Armored Core 6 Fires of Rubicon

The Ibis Series is a serious roadblock that players will need to overcome in order to progress through the main story of Armored Core 6. What makes this boss really tricky is its ability to easily shake off hard lock-on and airborne combat moves. The Ibis Series rarely, if ever, comes near ground level, making it really hard to target, especially for players with tanky builds.

However, given the C-weapon uses EN for most of its attacks, it is very easy to stagger, granted you're equipped with the right set of weapons to deal significant impact damage. Here are a few tips that should help you easily defeat the Ibis Series in Armored Core 6:

• In the first phase, try to stick closer to the boss. Equipping a mid or close-range FCS can help a lot in this boss fight.
• The Ibis Series always starts the fight with a barrage of laser attacks, followed by a single slash from its Coral Oscillator. All these can be avoided by simply quick boosting sideways.
• During the opening of the boss fight, quickly hard lock on to the boss and start shooting it with your shoulder cannons. If you time your shots correctly, you'll stagger the Ibis Series, allowing you to deal direct damage using your arm weapons (I highly recommend using Zimmerman or plasma rifles).
• Repeat these steps a couple of times, while also staying close to the boss (this helps you avoid some of its most damaging attacks, such as the Redshift slash, from triggering) to easily defeat the first phase.
• In the second phase, it gets a little tough to stick close to the Ibis Series. As such, it's best to stick to the medium range.
• The second phase has two new attacks that you need to look out for. The first is an extended Coral Oscillator slash combo, and the other is a special aerial combo, which is triggered only when the boss' health drops to less than 30%.
• Fortunately, both attacks can be dodged with perfectly timed quick boosts or assault boosting away from the boss.
• And if you time your attacks right, you can easily stagger the boss, right before it even initiates one of these special attacks.

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The Ibis Series is a challenging boss fight. However, with a properly optimized build and well-timed dodges, you can easily defeat the C-weapon. Once you defeat it, you'll be able to progress through the game's story and reach the final chapter of the game.