Oakensoul One-Bar - Lame noire Construire PvE - ESO

There are a few goals for this one-bar build:

1) Utilize Oakensoul Ring buffs

2) Utilize your back bar skill slots - Soul harvest generates 10 ult whenever you kill an enemy. Concealed Weapon gives you minor expedition increasing movement speed by 15%. Leeching Strikes converts 4k health for 2k magicka and stamina and heals you when you do damage. 

Like summons, the Banner Bearer skill is best when used on both bars, but since we are only on one bar, the cost of having it double slotted is reduced.

3) Use Power Overload ultimate as much as possible. Oakensoul gives you minor heroism generating 1 ult/1.5 secs. Chilling Trample gives you Major Heroism generating 3 ult/1.5 secs. Transfer passive generates 2 ult when you cast a siphoning ability every 4 secs. Catalyst passive generates 22 ult when you drink a potion. Eye of the Grasp generates 7 ult when you crit every 5 secs. Oakensoul also grants Empower increasing your heavy damage by 70% at all times.

The other benefit of using Power Overlord is that it helps with sustain; it allows you to go through your rotation setting up your buffs, DoTs, and HoTs, dump your resources into raw DPS, and then give your resources a chance to recover while melting enemies with your ult.

Skill Lines - 

• Assassination has two abilities that provide buffs from the backbar and the only ult that buffs from the backbar, and the other abilities are totally viable for the front bar as well. The passives are also very strong increasing crit chance, crit rating, crit damage, and sustain.
• Siphoning has one ability that buffs from the backbar, several great abilities for the front bar, and great passives for generating ultimate, increasing max magicka and stamina, and healing done. 
• Storm Calling has 3 passives that increase damage and the other helps with sustain. It has 3 great damage abilities, all viable for the front bar, and it's ultimate is a fun time and a core component of the build. 

These three skill lines combine really strong passives with slotted abilities that provide passive bonuses while on the backbar to create a flexible and powerful build that is easy and fun to play.

Skills - 

You need at least one assassination skill and one siphoning skill slotted. The other 3 are flexible and should probably be swapped depending on the content. See the breakdown below:

Ultimate: 

Power Overload - This was the inspiration for this build, but if you have access to Shooting Star, you could slot that instead and wreck face too.

Slot 1: 

We want an assassination ability slotted to gain 10% increased crit damage and Minor Savagery (increased crit rating) from Hemorrhage. Lotus Fan is a great as a gap closer dealing direct damage with an AOE DoT that applies minor vulnerability. 

Slot 2: 

We also want a siphoning ability slotted to increase max magicka and stamina by 6%, increase healing done by 3%, and generate 2 ult every 4 secs from passives. Swallow Soul and Sap Essence are both great spammable abilities that damage, heal, and proc Transfer. I think you could go either way and be effective, though Swallow Soul is better for individual enemies and Sap Essence is better for mobs. Swallow Soul is cheaper and provides better healing, so I tend to prefer it. (Note that Oakensoul already gives us the buffs provided by Sap Essence, so it's really just useful for the AOE damage and heals).

Slot 3: 

I also really like the Shocking Banner scribed skill. It increases your and your group's direct damage by 6%, grants minor resolve increasing your physical and spell resistance (which Oakensoul does not provide). The Class Script is difficult to acquire, so the third ability could be used for sustain or a damage shield. The Class Script would either restoring magicka and stamina or increasing crit chance by 10%. It helps with sustain, critting, and survivability, and you don't even need to cast it for it to stay active at all times. 

Slot 4: 

Shocking Soul deals great single target direct damage, DoT, and applies Major Vitality increasing your healing received and damage shield strength (which synergizes well with the damage shields from Warding Contingency and Shocking Banner. 

Slot 5 (Solo): 

Warding Contingency will give you a great damage shield, HoT, and applies Minor Breach. This is a really solid way to stay alive during harder solo content. For casual solo content where you don't need the shields or heals, you can get minor breach from Shocking Burst which also deals direct area damage and a DoT to breeze through fights.

*Minor breach and penetration from champion points and light armor passives are sufficient to negate almost all the resistance from overland monsters, so I went with Major Vitality on Shocking Soul instead of Major Breach.

Slot 5 (Group): 

For group content, your tank should already providing Major and Minor Breach, and your healer should be keeping your health topped off. So for Dungeons and Trials:

• Shocking Explosion deals significant shock damage, applies a DoT, and applies Minor Brittle increasing critical damage taken by 10%. This is the best way to reliably afflict enemies in a large area with Minor Brittle, so I think it's a really strong option for group content. The drawbacks are that is is expensive and there is a 2s cast time. I don't think sustain will be an issue with this build, so I'm not concerned about the cost. You can spam it against groups and when the adds are gone, switch to utilizing it more as a DoT and debuff while switching to spamming Swallow Soul against the boss. 
• Chilling Trample is a cool scribed skill that does high frost damage which scales with the size of the group. , but most importantly, it grants Major Heroism granting you 3 ult/sec which is huge. Casting this once every 10 secs will ensure you're constantly generating a lot of ult. 
• Unstable Wall of Elements is a great set-it-and-forget-it DoT option that will also set concussed enemies off Balance which is great for your lightning staff heavy and your Power Overload ult heavies. On a two-bar build, I would use it, but for one bar, I think I prefer Shocking Explosion or Chilling Trample. It also just doesn't benefit from the direct damage buffs from Champion Points and Shocking Banner (which I admittedly am not recommending using unless you have access to the Class Mastery Script).

A constant 6% direct damage buff from Shocking Banner is nice, but the damage shield and minor resolve from it is likely redundant and unnecessary. I would recommend swapping Warding Contingency and Shocking Banner for Shocking Explosion (for DoT and brittle) and Chilling Trample (for AoE spam and Major Heroism). 

Equipment - 

1 Oakensoul

5 Eye of Grasp for ult gen

1 Slimecraw for crit chance

The other 5 piece could be Werewolf's Hide for ult gen, Grave Inevitability for 20% more crit damage, or Kinras's Wrath for Major Berserk which gives you +10% dmg. I prefer Grave Inevitability given all the ways we are boosting crit chance and crit damage throughout the build.

For a starter set that's easy to craft, I like Order's Wrath to increase Critical Chance, Critical Damage, and Critical Healing.

*There are other skills that provide a buff when slotted on the back bar. They were considered but weren't included since the buffs are redundant with Oakensoul - Merciless Resolve, Bound Armaments, Cauterize, and Flames of Oblivion are a few, but there are more.