Quick Summary
Cast Summon Wraith, Infernal Shade and Dread Shade on it, and transplant around to move your minions and avoid damage.
Gameplay
After entering a new zone, re-cast summon wraith, and put both shades on it. Shades can sometimes drop off when changing zones.
Use Transplant to maneuver the wraithlord and control where its damage goes. The wraithlord does not move on its own due to Locus Of Death 1/1, so the affix PrefixExperimental Minions Transported with Traversal Skillsis required. You can drop locust of death, but it massively reduces damage and means you cannot precisely choose where the wraith is attacking.
Transporting into enemies works due to Thanatophobia 1/1, which fears targets where you appear. However, this impacts each target only once, so do not expect teleporting into a boss multiple times to cause multiple fears. This allows you to put the wraithlord in the proper position for dealing the most damage while also buffing its attack speed due to Veins of Malice 5/5. Keep the wraithlord out of AOE attacks as much as possible. It can tank most attacks and heal itself, but when playing over corruption 1,500, incoming damage is so high that it will die to AOEs. This can result in a 90% loss of dps if you recently cast Dread Shade.
For even higher damage in boss fights, keep the wraithlord and two normal wraiths close to the boss, with Infernal Shade on all 3 minions. This will apply 80-100 armor shred stacks, boosting damage against tanky enemies.
Cast Bone Curse every 6-8 seconds on bosses or large groups of enemies to apply Marked For Death and Slow, boosting DPS and making it easier to avoid incoming damage. Idols can also allow minion attacks to provide marked for death, but idol marked for death is not ideal against groups. Bone curse applies it to every enemy in the AOE, and having marked for death applied to every target can be the difference between a 1-shot and a 2-shot.
Potion cast speed buff - Elixir of Hunger 8/8. This node buffs your minion attack speed by 10% for 8 seconds after taking a potion. This is directly a 10% damage buff on potion use, and you can have it always active in monoliths as well as boss fights. Potions also boost movement speed due to Exsanguinous, resulting in consistently high movement speed.
Wraithlord mechanics
Wraithlord scales with Summon Wraith and shoots necrotic beams when not summoning other wraiths. This build focuses on that necrotic damage, so we want to summon the only 2 small wraiths to maximize the wraithlord's time dealing damage. Twin Spirits 1/1 reduces the max small wraiths to 2. Any other summons are targeted by the wraithlord, giving it a temporary damage and health boost. Using Simulacrum 1/1 allows you to consistently feed the wraith and keep the buff up.
Optionally, you can take Bone Prison 1/1 and Shattered Prison 1/1 to feed the wraith. This reduces dps but boosts wraith health. it shouldn't be used with simulacrum because that reduces DPS further, with no additional benefit.
Bone Curse mechanics
Bone curse applies a curse which deals damage per attack on the target, making it a decent damage boost on top of high direct attack speed builds. However, the main reason I use it in this build is for marked for death Sigil of Mortality 1/1, slow Crippling Anguish 2/4, and kill threshold Brittle Bones 3/3.
Marked for death boosts damage of the wraithlord, and slow prevents swarms from overwhelming you.
Flame Wraith mechanics
Flame Wraith is a decent buff to the small minions because it scales with fire damage and can hit from range, making them useful during wave clear or fights where you cannot stand on the boss. They can also apply marked for death with an idol, providing a higher uptime on the debuff against bosses. I use one idol withPrefixChance for Summon Wraith to summon a Flame Wraith instead and health on it to improve the chances of getting a flame wraith.
Dread Shade mechanics
Dread Shade is used for buffing the wraithlord and is responsible for over 70% of the damage done. I take Egoism 1/1 for 100% crits, Blind Fury 1/1 for faster attack speed, and other nodes for damage buffs. Optionally, you can go into Pernicious Pact 1/1 and Doomed Wrath 3/3 for maximum damage, but this deals permanent poison damage to the wraith which will eventually kill it. An easier way to play this build is using Duskheart 2/4 and Flesh Harvest 2/3, which results in a bit of a damage loss, but the wraith doesn't have to die and be re-summoned.
Infernal Shade mechanics
Infernal Shade is a great buff to minions, improving their attack and cast speed, directly improving dps and wave clear. It also applies Shred Armour, boosting dps against bosses and high health enemies.