Gibbering Shield
(Useful)
The primary benefit of Gibbering Shield is its Wellspring of the Abyss passive, granting an addition to all recoveries when slotted. If your goal is Magicka Recovery only, Barrier combined with the Magicka Aid passive is a more effective option.

This can be used as a Shield/Defensive skill for emergencies or while using Saxhleel Champion but Barrier is a superior choice for this purpose.

Runic Sunder → Morph of Runic Jolt
(Useful)
When applied to an enemy, it taunts and inflicts an armor penetration debuff of 2200. Combined with Tremorscale, it can potentially replace the need for Crimson Oath’s Rive and Alkosh in groups where they are needed. This skill is particularly beneficial in dungeons and arenas, as your Damage Dealers might not be at the penetration cap. Additionally, Runic Sunder “steals” armor from the enemy, granting you 2200 armor and boosting your own resistances. It also applies Minor Maim to the enemy, generates a Crux and provides a 2% damage reduction while slotted.

Impervious Runeward → Morph of Runespite Ward
(Vital)
Impervious Runeward is a crucial damage shield and one of the most vital Arcanist survival tools, as it also provides healing. This morph is preferred for its reactive nature, offering a larger shield initially and a smaller one afterward. Unlike the other morph, which consumes Crux to reduce the shield’s cost, this one allows for frequent casting without cost reduction due to the Arcanist’s substantial recovery potential. The healing effect scales with the amount of Crux saved, making it the most useful Crux spender for tanks, providing a substantial heal when needed.

Cruxweaver Armor → Morph of Fatewoven Armor
(Vital)
This is the preferred morph of this skill due to its longer duration and ability to generate Crux, as opposed to spending it. Fatewoven Armor grants Major Resolve and also applies Minor Breach to enemies when they hit you, making it exceptionally useful in dungeons for easy application of Minor Breach. This allows you to potentially drop Pierce Armor entirely and rely on Runic Sunder, as Minor Breach is already covered. For Major Breach, you can use skills like Razor Caltrops or Weakness to Elements.

Unbreakable Fate → Morph of Fatewoven Armor
(Optional)
This alternative morph provides additional Block Mitigation but consumes Crux to do so. It’s better to limit Crux-consuming skills to just one for better control, and the additional 5% Block Mitigation isn’t substantial. However, if you’re struggling to survive single-target or AoE damage, this morph can be useful. Just ensure you’re building up Crux before using it to gain the full benefit.

Runeguard of Freedom → Morph of Runic Defense
(Optional)
This multifunctional skill provides an automatic heal if it is still active when your health drops low. It also offers a group buff of Minor Resolve and grants you Minor Protection, which is consumed to trigger the heal if needed. This morph is generally better for Trials, as it provides additional resistances and CC immunity when your health is low and the heal procs. It is especially useful in boss fights where immobilizing enemies isn’t usually possible, making this morph more valuable for trial content.

Runeguard of Still Waters → Morph of Runic Defense
(Vital)
This morph is particularly effective for dungeons, arenas, and add pulls, as it immobilizes up to 6 nearby enemies in a 360-degree radius. It retains all the benefits of the other morph, including the automatic heal, group buff of Minor Resolve, and self-buff of Minor Protection. The added crowd control is especially useful after using Void Bash or any chain skill to keep enemies rooted in a tight stack, making it a superior choice for these scenarios.

Rune of Uncanny Adoration → Morph of Rune of Eldritch Horror
(Vital)
The Arcanist lacks a traditional pull skill, but this Charm ability effectively pulls and stacks enemies. Unlike other crowd control abilities, Charm is a unique and powerful mechanic in ESO. Casting this on a ranged enemy causes them to run to you and follow you for 8 seconds, making it a sustainable alternative to Silver Leash, as it uses Magicka. However, it has a limited range of 15 meters and cannot be used on Elite enemies or those already stunned/immobilized.
This skill is essential for dungeons. While Void Bash can stack enemies, any that are missed can be charmed into the stack with this ability. A key advantage is that charmed enemies are bound to you and unable to cast abilities for 8 seconds. To prevent unnecessary movement, it’s beneficial to immobilize enemies after charming them. This combination ensures efficient crowd control and positioning.

Rune of the Colorless Pool → Morph of Rune of Eldritch Horror
(Vital)
This skill is crucial in trial scenarios, providing significant DPS benefits. While the other morph is preferred for dungeon content, if you use Silver Leash or another pull ability, this morph excels especially against bosses.
This morph grants a long duration of Minor Brittle and Minor Vulnerability, enhancing group DPS. Notably, it allows you to apply Brittle without using an Ice Staff, offering a new and sustainable way to maintain high uptime on this debuff.

Aegis of the Unseen
(Vital)
As long as you have a Soldier of Apocrypha skill active, you will benefit from the added resistances.

Wellspring of the Abyss
(Vital)
This passive is incredibly powerful. For each Soldier of Apocrypha skill you have slotted, you gain more of all recoveries. Since all Soldier of Apocrypha skills are useful for a tank, this can result in substantial recovery gains, and this increases further with percentage modifiers. 

Circumvented Fate
(Vital)
This passive provides a group buff of Minor Evasion, offering a small survival benefit by reducing Area of Effect damage. Although it is situationally useful, it becomes valuable in content with significant AoE damage, enhancing the overall survivability of your group in such scenarios.

Implacable Outcome
(Vital)
This passive grants additional Ultimate gain when you use Crux, allowing you to cast your main Ultimate more quickly. Any increase in Ultimate generation is highly beneficial.