Tips for fighting against Messmer The Impaler In Elden Ring

For the first phase he has that spinning attack - 4 hit combo that can be dodged with front rolls and the final hit with jump.
other attacks also include circular fire spreads and charged spear attacks

Charged spears sidewards or backwards.
Fire spreads fornt roll.
there is also a front spear followed by a delayed spear atatck thats difficult to dodge. You'll have to time to second one and dodge at the opposite (left) direction. Other directions may work as well but havent tested it out.
other Phase 1 attacks are easier to dodge. Front Rolls are your best friends.
Also he starts phase 1 with a massive fireball atatck taht can be avoided with front roll as well and has huge punish window


Phase 2
He starts with fireball again. Punish it.
then he summons snakes that can be avoided side ways. His huge phase 2 atatcks are the ones where he covers the area with snakes and spiral attack. Go backwards for that multiple snake hit attacks and dodge side ways for the spiral. Rest of the Phase 2 is same as the first one and also he is gets slightly more agressive.

Using a fingerpirnt shield and bullgoat armor can help f you want to tank hits and trade blows. Just make sure to get the damage to negation to optimal levels by gathering as much scadu tree fragments as possible.

good luck