[Voruna] is actually a very strong melee frame, despite what ignorant people who tout Ulfrun's Descent as her strongest ability might try to convince you to believe.

Shroud of Dynar is insanely strong. It is a multiplicative increase to your melee crit multiplier and will cause you to do insane amounts of damage, on top of giving you guaranteed melee crits and slash procs. You can essentially turn pretty much any melee into a powerhouse.

Due to Lycath's [Hunt], you can slot [Equilibrium] and spam abilities indefinitely. This is extremely powerful in combination with [Brief Respite] (or Augur Set Mods) and [Catalyzing Shields], as you can infinitely shield gate all damage coming your way, save for toxin/venomous eximus enemies in Infested/Corrupted Arbitrations and Steel Path. I'm aware that Shield Gating isn't popular anymore, but it's still strong in all content if you play smart.

250 kills with [Molt Augmented] will give you an even bigger multiplier for Shroud of Dynar, which I would strongly recommend. As for the other arcane, [Arcane Fury] is a solid choice for nearly triple your melee base damage, but there are definitely stronger (though more expensive) options, like [Arcane Arachne].

You also don't need [Adaptation], [Rolling Guard] or [Primed Sure Footed], because [Voruna]'s passive ability from Fangs of Raksh makes you completely immune to negative status effects. Speaking of, [Archon Continuity] will not only make the first and third abilities last longer, but will also give Fangs of Raksh a sixth stat proc when it procs Toxin, strengthening mods like [Condition Overload] even further without needing to recast as much.

Unfortunate as it is, Ulfrun's Descent is simply not a good ability in the slightest for Steel Path when compared to other options such as the [Xoris], and should be replaced with a good subsume. I personally recommend [Wisp]'s Breach Surge because good crowd control makes this build even crazier, but there are other options as well to simply increase your damage output. For instance, you could use [Kullervo]'s Wrathful Advance for a huge critical chance increase, plus it can work off of Tennokai.

I am lazily editing this portion in to clarify something regarding [Voruna]'s 4th. What people like to say about it is it nukes in Steel Path because it does massive slash procs to huge groups of enemies when you prime them with her 2nd. This is not true, her 4th isn't nuking at all, her 2nd is. Her 4th on its own can only kill one at a time with its slash ticks unless the enemies are right on top of each other, it's the 2nd that kills crowds, her 4th has garbage AOE damage. You can achieve the same result using her 2nd and any well-built melee that capitalizes off of her melee critical damage bonus, but far better AND a lot faster. Replacing her 4th with good CC makes her far more viable for Steel Path and especially endurance runs. The reason why I recommend Breach Surge is because it does massive damage and makes room clears faster, as well as landing headshots to force Energy drops from her 3rd. Literally dropping her 4th and relying on your melee weapon turns her into a monster.

The exilus slot is more of a flex spot for whatever you choose to strengthen by a small amount. I prefer [Power Drift], but [Cunning Drift] is also good. If you want interchangeability, you'll unfortunately have to use an Umbral Forma with this build.

I HIGHLY recommend combining this build with Archon Shards. A single Tauforged Azure Shard combined with four Violet Shards will increase your melee's critical damage multiplier by a lot, and with Shroud of Dynar it can increase your multiplier into the 70s-90s with both crit damage mods on your melee.

This is in my opinion as someone who has dedicated ~700 hours into playing [Voruna], one of, if not THE strongest build for this frame. It's a solid all-purpose build, excelling in all mission types, offensive defensive and stealth. I've carried countless missions with this, constantly taking ~95% of the damage dealt with the most kills, the only exceptions being any time I've played with nuke frame teammates or played long runs of Steel Path with my buddies who also have endurance builds, the latter usually ending with our stats being relatively even. I believe it to be crushing in endurance runs, having tested it in Steel Path Circulus for a few hours and it held up just as good at the end as it did at the start.