Mechanical Function
Marcus uses Multistrike to proc Forge Strike several times in a singular encounter. The Forge Strike then gives us 40% chance to summon a Summon Forged Weapon on a singular enemy. Hitting multiple enemies with it will obviously cause more to form. Mathematically we have a 100% chance to proc when hit 3 enemies or more. (However RNG doesn't always work like that) When it come to bosses or rares, we have a 85% chance to summon a weapon. This is up to a maximum of 12 Summon Forged Weapon's. These minions will last for 32 Seconds, and can be resummoned at rapid rate, and will reset their lifespan. You also have a 20% when you forge a weapon to summon a great axe with the Forgemaster node. These have the same damage, but they have increased area range. After taking the Engines of War node, these axe's will have 110% increased AOE cleave, our generic minions will have 60% increased area cleave. The Multistrike will also proc Smite, which is used mostly for healing (minions and us) however, we also have it apply Ignite and a chance to cast Spreading Flames with Holy Fire and Immolate. We also use Smite to pump our attack speed by 20% with Righteous Flurry. This is not to pump OUR dps, but to increases the rate at which when drop Forge Strike on people heads.
Offensive Mechanics
The offense for this build is our minions. So I will instead talk about the functionality for them.
Manifest Armor - The manifest armor uses the stats from various pieces of gear that we roll on his skill tree. We specifically are targeting him to use our gloves, sword, body and helm. However, with amplified gains for the stats on each corresponding item. For the body, he uses 160% of the stats (no unique mods). Gloves 240%, Helm 240%, and the sword (no bonus % for sword). We do give him a significant buff of damage with Redistributed Steel and Force of Impact. This can be significant to us, because for every 10 points of armor we have on it, he gets +1 Melee Physical Damage, this is AFTER the 160% increase. This can add 105 Melee physical damage to him if rolled perfectly, or at the minimum or 94 if bottom rolled. Since he is using OUR Odachi, he is gaining the multipliers and attack speed. Keeping him alive is relatively simple because of our Ribbons of Blood. The gloves he uses at 240%, and since the gloves have PrefixMelee Attack Speed, and SuffixIncreased Leech Rate, at more than double of the face value of the affixes (it gets a little ridiculous). This is why we HAVE to have Solarum Bracers, for the implicit of critical strike chance. The helm is more for us than him, but he does benefit from armor bonus but not the bonus per forged weapon. The Summon Forged Weapon are YOUR, not HIS. He also gets to take advantage of Death Rattle which will give him up to 100% critical strike multiplier.
Summon Forged Weapon - These only take the benefit from the sword, Death Rattle and Ribbons of Blood. However, since the sword has a + to the base critical strike chance, attack speed, and ignite. The also benefit from the weapons implicit (melee damage and critical strike multiplier).
Defensive Mechanics
We are mostly reliant on armor from our Sunforged Greathelm, and Dawn Plate. The Advent of the Erased and Code of an Erased Sentinel will help us take care of those pesky DOTs we can run into from time to time. It would not be uncommon to see your armor hit the 10,000 to 15000 range. You will continuously see yourself at the armor cap of 85% thanks to the unique modifiers in Sunforged Greathelm (10%-12% increased armor per Summon Forged Weapon AND 2 - 5 HP regen per Summon Forged Weapon) considering this is up to 12, which it is very common to have 12, this is a significant boost in regen and armor. As always, it is still smart to dodge obvious high damage mechanics when available. Smite is used for us and our minions as well. Since we engage at a melee distance, majority of our Smite's will hit us and them.
Mana Management
We gain mana per Multistrike, and since we stack so much PrefixAttunement, we have a large mana pool. If this does become a problem (It should not, I extensively tested it live on stream several days) You can take a point out of Blademaster and cap the Time and Faith node. This swap to slow our attack speed and increased our mana gain should equalize the in and out flow of mana.
Basic Engagement
We start almost all encounters the same way. Resummon your Manifest Armor if he's low. Cast our "casual" (unscaled) Ring Of Shields. Lunge into a pack and hold down our Multistrike skill. You can press Lunge again to engage immediately (we have 2 charges and have 30% cooldown reduction with Valiant Charge)
Skill Interaction Note
Multistrike will not proc Smite on a singular target. Be aware of this in any engagement. You can "fool" the proc, by either swinging the sword away from the enemy or by standing too far to hit it. By doing this you will not gain stacks to drop Forge Strike though. So if you don't have any minions, don't worry about Smite, it doesn't do much damage for us, it's primarily used as a heal for the minions.
Difficult Engagement / Bossing
No real change from our standard engagement. However, you may want to balance backing away to make sure Smite procs, and getting close enough to drop Forge Strike from the Multistrike. (watch the demo video, I use this tactic)