Mortar Scrapper 2.0

This build is viable for up Chaos 9 solo and even Chaos 10 but I recommend doing C10 only in a group or when you really need that extra EXP. The main ‘ingredients’ are the Powder Heir set that grants us the Heroic Mortar skill + Recycling Mastered + preferably a Mountain Pendant and/or Fiery Ring of Thori for CDR procs & a Siegebreaker Ring for a nice dmg burst. Recycling Mastered gives us a nice dmg buff as long as we keep the 10 stacks up and it also constantly lowers our cooldowns while collecting scrap as well as regenerating energy if we choose to use Heavy Pounding more often. The blessings used are the combos for counter attack damage +hp+armor with more hp than armor for some pieces and for other pieces the dmg+hp combo more dmg gems. There is more wiggle room for customization of the skills/passives with the Challenge set. NOTE: The build requires owning the God Skills DLC (& the Season Pass if you decide to use Hero of the Desert).

Build Video footage:

The gear I recommend using is:

•  the Powder Heir set (Powder Carrier)
• one of the following Hammers:
  • Rocksplitter – 100% melee attack dmg + 20% dmg reduction after a melee attack for 3 secs
  • Forge Heart – grants a fiery aura based on overheating level + overheating explosions generate a huge wave of fire
  • Stonebreaker – Crit dmg and chance are increased if overheating is low (when under 20 heat this seems to give 200% crit dmg and 20% crit chance)
• a Corroder Pistol [until Forgeblood is fixed] (gives 200% dmg when hitting enemies that are in the moving circle)
• Mountain Pendant (cooldown decrease + energy regen) [OR Bloodstone Pendant for god skill heals or any other good rolled]
• Fiery Ring of Thory Ring for cooldown reduction procs (or other of your choice with good rolls)
• Siegebreaker Ring for dmg + cooldwon decrease (or other of your choice with good rolls)

The recommended stats to look for in each item are:

For the Helmet:

• Cooldown Reduction (highest priority)
• HP (high priority)
• Armor (high priority)
• Cost Reduction (mid)
• Health regen (mid)
• Resistance to DoT (mid)

For the Chest & Leg Armor:

• HP (highest priority)
• Armor (high priority)
• Cost Reduction (mid)
• Health regen (mid)
• Resistance to DoT (mid)

For the Boots:

• HP (highest priority)
• Armor (high priority)
• Movement Speed (high/mid priority)
• Cost Reduction (mid)
• Health regen (mid)
• Resistance to DoT (mid)

For the Gloves:

• Damage (highest priority)
• HP (high priority)
• Damage over Time (high/mid priority)
• Armor (high/mid priority)
• Crit DMG (mid priority)
• Cost Reduction (low priority)
• Health regen (low)
• Resistance to DoT (low)

For the Pistol:

• Crit Chance (highest priority)
• Cooldown Reduction (highest priority)
• Damage (high priority)
• Cooldown Reduction (highest priority)
• HP (high priority)
• Damage over Time (high/mid priority)
• Crit DMG (high/mid)
• Armor Piercing (high/mid priority)
• Health Drain (mid)

For the Hammer:

• Damage (highest priority)
• Cooldown Reduction (highest priority)
• HP (high priority)
• Crit DMG (high)
• Damage over Time (high/mid priority)
• Armor Piercing (high/mid priority)
• Health Drain (mid)

For the Amulet & Rings:

• Crit Chance (highest priority)
• Cooldown Reduction (highest priority)
• Damage (high  priority)
• HP (high)
• Damage over Time (high/mid priority)
• Armor Piercing (mid)
• Crit DMG (mid)
• Health Drain (mid)
• Armor (only rolls on amulets- mid/high priority)

The Skills and Passives I recommend are:

Version 1: Regular Setup

• Heavy Pounding Mastered (decent dps source + procs the Rocksplitter hammer)
• Mortar Heroic (main dps source for nice bursts of dmg)
• Move Mountains basic (nice dmg reduction + a bit of AoE dmg + can stun)
• Makeshift Automaton Superior (decent additional damage + used to build duelist’s chain reaction stacks)
• Explosive Rush basic (our mobility skill + can build duelist’s chain reaction stacks)
• Engineer of War Mastered (dmg reduction buff + heal + armor piercing buff)
• Recycling Mastered (up to 50% dmg buff [at 10 stacks] + constantly lowers our cooldowns while collecting scrap + regenerates energy)
• Upgraded Radiator Basic (dmg reduction based on overheating level)
• Hero of the Desert (a bit of everything) [if you don’t own the Tomb Kings DLC swap it for other]
• Upgraded Automatons Superior (+2 max turrets + dmg reductioin buff for us + CDR for the turrets)
• Duelist’s Chain Reaction (up to 400% crit  dmg which is 4 stacks of 100%)
• Alternating Pistons Mastered (alternates between 20% dmg reduction & 20% dmg buffs + reduces cooldowns while alternating) [OR superior/basic if you need points]

Version 2: For speed running lower Chaos levels

• Heavy Pounding Mastered (decent dps source + procs the Rocksplitter hammer)
• Mortar Heroic (main dps source for nice bursts of dmg)
• Move Mountains basic (nice dmg reduction + a bit of AoE dmg + can stun)
• Makeshift Automaton Superior (decent additional damage + used to build duelist’s chain reaction stacks)
• Explosive Rush basic (our mobility skill + can build duelist’s chain reaction stacks)
• Engineer of War Mastered (dmg reduction buff + heal + armor piercing buff)
• Recycling Mastered (up to 50% dmg buff [at 10 stacks] + constantly lowers our cooldowns while collecting scrap + regenerates energy)
• Upgraded Radiator Mastered (dmg reduction based on overheating level + 100% dmg for the overheat explosion) [OR superior/basic if you need points]
• Scout’s Chain Reaction (30% movement speed for 4 sec. after using a cooldown skill)
• Upgraded Automatons Superior (+2 max turrets + dmg reductioin buff for us + CDR for the turrets)
• Duelist’s Chain Reaction (up to 400% crit  dmg which is 4 stacks of 100%)
• Alternating Pistons Superior (alternates between 20% dmg reduction & 20% dmg buffs + heals while alternating]

The God Skill Tree has one version that uses both trees: