A regular build for a Tridolon Harrow, with a guide to how to use it.
I don't give a crap about "4x3;5x3;6x3" - this only depends on your entire team's setup, not about 1 individual, as for how successful you will be on a single night playthrough. Period.

Lets start, shall we?

This build is focused upon fast and impactful eidolon resistance buffings, during it's howl/shout and whenever it is needed in action. You are not the main damage dealer (though, you can be, when using Snipers with good Rivens + weapons like [Sarpa] with [Shattering Impact] stripping off armor), you will mostly focus on being a supporter in all terms.

On every [Howl] (called Energy Spike), try to match your Covenant ability on time, whenever the Eidolon is initiating its attack.
Keep in mind, there is more than just one AoE attack.
If possible, try to get the Lures and hand them over to a Trinity.

This is more a beginner/intermediate friendly build. You can also swap [Steel Fiber] and [Vitality] for their Umbral versions, but this will require a few more Formas here and there.

You can also change Arcane [Guardian] to anything you like more. Arcane Nullifier is a must, imho.

There is nothing more to explain. The Tridolon fight itself is another story!

Happy hunting, Tenno.

Best regards,
Pacheon