Mortal Shell II How to Beat Sir Isaac
Phase 1 is readable. Phase 2 is where most runs end. Here is the dodge-first strategy, the best Shells and Seals, and the mistakes that kill your attempt.
Surviving Phase 2 is the entire fight. Phase 1 (sword and shield) is readable if you parry and stay off the shielded side. Phase 2 (shield gone, multiple blades, long combo strings, leaping lunges, pin-cushion thrusts, whirlwinds, and fake-outs) is where most runs end. Double and triple hits often punish a single parry, dodges feel tight, and a few abilities can make him stop taking damage. Get him to half health without getting greedy, then stay alive through the multi-blade strings by dodging first and only taking 1-2 hits after a combo ends.
1Phase 1 - Shield Up
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1
Put the sidearm away. His shield eats ranged shots.
Strafe to his unshielded side and work melee.
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2
Parry the readable sword strings
Respect the fast point-blank shield bash. Do not mash parry into it.
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3
After a combo finishes, take one light or heavy, then reset
Do not riposte every opening if you are trying to stay safe. Some players report the half-health riposte is where the fight gets messy or bugs.
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4
Do not use Sariel's thorn ability here
Multiple players found he becomes invincible in Phase 1 after thorns, even after multiple ripostes.
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5
Grisha Remnant summons help a lot in this phase
They eat pressure and add stagger. Keep them up if you have remnants.
2The Phase Transition at ~50%
3Phase 2 - What Actually Works
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1
Switch mindset: dodge first, parry second
Long 12-hit strings and "parry one sword, eat the second" are the main killer. Players who beat him after 20+ tries describe mashing dodge on Tiel or pairing Proxima's Grafted Armor with Infinite Seal parries.
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2
Tiel: stay mobile and spam dodge through the whirlwind and teleporting strings
Several posts call this the shell that made Phase 2 click.
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3
Proxima: Grafted Armor procs let you eat a hit you should not, then keep dodging
Pair with Infinite Seal. Its slightly different parry timing builds stagger faster if you can retrain the timing (about 2-3 frames tighter).
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4
Keep mid-to-long distance when he winds up Leaping Lunge or Pin Cushion
Pin Cushion is repeated downward rapier thrusts. One or two connections in this form often kill. Punish only after the chain ends.
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5
If he suddenly stops taking damage, stop parrying and using abilities
One player recovered by dodging and swinging only until damage registered again.
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6
After a string, one or two hits max
Greed is how Phase 2 ends attempts.
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7
Keep Grishas up if you have remnants
Community consensus is they are "broken" for this fight.
Fight Demonstration
Common Mistakes to Avoid
- Treating every opening as a riposte window at the phase change. The transition is messy. Play safe.
- Using Sariel thorns in Phase 1. He becomes invincible. This is a known soft-lock.
- Standing in front of the shield and dumping ranged. His shield eats ranged shots. Go melee from the unshielded side.
- Trying to parry both hits of a double or triple instead of dodging the follow-up. Dodge first in Phase 2.
- Staying close during Pin Cushion or whirlwind. Back off and punish only after the chain ends.
- Expecting the official "skip Phase 2" line to work. Players report still getting Phase 2. Treat it as required.