This guide is based on the post-buff kills of Valax by the US3 Legends guild.

Introduction

Valax is the 4th and final boss of the Tower of the Storm Frontier Zone. He is labeled as a Realm Boss (the first of his kind) and drops 10 Elder Fragments, as well as some Hexeye, upon a successful kill. He also has an increased chance of dropping legendary gear and a chance of dropping an exclusive mount.

In order to reach Valax' domain, you need to assemble an item called the Storm Lord's Beacon. The Beacon has 3 uses and a 1 day cooldown. Using the Beacon in the main hallway of the Tower of the Storm will create a portal to reach Valax.

Assembling the Beacon

Crafting the beacon is a large undertaking; it requires materials that will ask you to gather and craft a lot of materials, as well as run a ton of Frontier Zones and max out your reputation with the Ardent Altruist faction. Because of this, it will usually be a guild or server-wide task to assemble 1 Beacon.
In order to craft the Beacon, your smithing level needs to be at least 85 and you need to be trustworthy (150/150 reputation) with the Ardent Altruists to buy the Storm Lord's Beacon recipe from Cedric Fairbarn at Kingsport for 3000 Altruist Seals.

The materials for the Beacon are the following:

Please note that everything listed here except the recipes, Altruist Seals, Elder Fragments and Expedition Caches is tradeable so you can have different people contribute to the Beacon craft. Once you have you the Beacon assembled you are ready to challenge Valax.

Valax strategy guide

Valax is a 4 phase encounter that takes place in Valax' Lair. Keep in mind that if you die during the Valax encounter and don't use a Voltan Resurrect you will have no way of getting back to the fight as the portal despawns after a while.

Phase 0 at 100%

Does nothing noteworthy aside from doing an AoE Shadow Blast around himself and raining down multiple shadow meteors across the entire arena. Pretty much just a tank and spank.

How to beat this phase

You need good defenses to withstand the damage from the blast, dodge the meteors. Pretty straightforward.

Phase 1 at 90%

Summons 6 Weary Souls (3 on each side) that heal the boss and damage players. These stay up for 60 seconds, after 60 seconds have passed all living Souls get consumed by the boss which heal him for a fraction of his HP per Soul consumed. When the Weary Souls get below 25% HP, their HP bar freeze after which you need to hit them with burst damage. When they die, they cast an AoE Corrupting Plague around them (DoT with Magic Resist debuff). After this there is an intermission phase of 15 seconds where you have time to chip away at his health, after which he will summon 6 Weary Souls again. He repeats this pattern until you push him below 60% HP to start the next phase.

How to beat this phase

The hardest phase of the fight and a real DPS check. Your group needs to strike a balance between damaging the boss and killing the Souls in time. If you don't have enough DPS it can be easy to stay hard stuck here and don't progress further, however as long as you dealing more damage to him than he heals per Souls and Intermission cycle you will eventually get there.
A helpful, but risky strategy is to gauge your group's overall DPS to determine how many percentages of his HP you can reduce in 1 minute so that you can skip the final Soul sub-phase as all Souls automatically de-spawn once he hits 60%. So if you know that, for example, your group can deal 15% of his HP in 60 seconds and the boss is at 75% or lower at the start of the Soul sub-phase, your group can focus fire the boss and ignore the Souls to start the next phase before he consumes them.

Phase 2 at 60%

He spawns a purple circle, that deals damage if you stand in it, in 1 of the 4 corners of the arena every 15-20 seconds. The circles are rather big (1 circle covers around 20% of the arena) but they move slowly. This phase ends once the boss has 25% HP.

How to beat this phase

Another DPS race, although not as hard as the previous one. Potentially lethal as the arena will be eventually covered in circles but you shouldn't struggle with this phase since you beat phase 1. Just have your entire group dodge the circles and DPS the boss.

Phase 3 at 25%

Valax goes immune in the center of the arena and summons differently colored Weary Wraiths around him. All Wraiths need to die before he can be damaged again. They also have Templar and do a shadow AoE around them for 20 seconds which damage people standing in them. This AoE becomes bigger every time a Templar dies. This phase ends once all Wraiths are dead.

How to beat this phase

Since they all have Templar, your group needs to establish a kill order for the Weary Wraiths to avoid any unnecessary healing by them. Stay out of the shadow AoE.

Phase 4 at 25% (right after P3 ends)

He creates a barrage of shadow projectiles which covers the entire area and does overlapping damage. Multiple yellow barriers will spawn across the arena where you can take cover from the projectiles. He repeats his shadow barrage attack every 20 seconds until he is dead.

How to beat this phase

This is the deadliest phase, as tanking 1 barrage will kill you. The only way to not die, aside from immunity spells, is to take cover in 1 of the multiple barriers that appear across the arena. What makes this phase especially deadly is that the barriers can de-spawn in the middle of his shadow barrage attack. In order to avoid dying to this, make sure to always move to the most recent barrier as soon as possible in between shadow barrages.

I hope this guide is helpful for any future Valax attempts. If you have any questions or comments, please leave them below.