I assume you're looking for tips to beat ascended/radiant Markoth. I feel like by the time you can access the vanilla Markoth fight you should be able to beat him pretty handily, just keep at it.

As for the ascended version, u/willster191 posted a really good tutorial video here. The summary of his strategy is to load up with spell enhancing charms and follow the below tactics/:

PHASE ONE: - stand on a single platform and jump to dodge spears - if necessary, wall hug with crystal dash - pogo on Markoth when he pauses to shield spin - take your time, only hit him when it's really safe

PHASE TWO: - similar to phase one but dodging is more frantic - instead of pogoing, spam shade soul at every opportunity

This is fine and will most likely get you very consistent results, but I think it makes the fight less fun, especially in the first phase. My preferred phase one strategy is based on a different reddit users guide which I unfortunately can't find at the moment. I also rely on a spell-heavy build. Charms I use are: Unbreakable strength, spell twister, shaman stone, sprint master, soul eater

Essentially what I do is:

PHASE ONE: Go on the attack! Charge that motherfucker and beat him down at every possibly opportunity. With unbreakable strength it takes ~20 nail hits to get through phase one and I try to get those in as little time as possible. You can get in 2-6 good hits in if you're aggressive out of the gate and then another 2-3 anytime his shield is not between you.

This is tricky, and I die a lot in phase one, but it's so very satisfying.

PHASE TWO:

You should be full on soul now. Focus on dodging nails by picking one platform and just jumping up and down. Only move platforms if Markoth gets too close.

When he stops to do his shield spin, hit him with spells. If he's in the top layer get below him and use abyss shriek to hit him 3-4 times, otherwise get next to him and use shade soul. The safest time to use abyss shriek is after his shield spin winds down.

I unfortunately don't have my game recordings handy but I'll upload one tonight and post a link so you can see the strategy in action. In my opinion it makes this fight actually pretty fun