Pass the Fear Weapon Parts Guide: Picking a Battle Skill

A part is a passive plus your Battle Skill

Every one of the 49 weapon parts carries two separate effects. The passive runs constantly while the part is installed. The active effect is your Battle Skill, the ability you press.

That second half is the one players underrate. Your Battle Skill is not a character ability with a fixed identity. It is whatever part is currently on your weapon. Installing Deep Winter gives you a Frost Grenade for 300 Frost Battle Skill Damage. Installing Heavy Magazine instead replaces it with an instant full reload. Same hunter, same gun, completely different button.

Browse the full list with both effect lines on the Weapon Parts database.

Read the active effect before the passive

A passive is a percentage. A Battle Skill is a tool, and it decides what you can do when a fight goes wrong. Sort the actives by what they solve:

• Damage on demand: Soul Shock, Deep Winter, and Vintage Barrel fire a 300-damage elemental shot. Deadeye fires a piercing Spiral Bullet for 550 Physical Battle Skill Damage.
• Reload and ammo fixes: Heavy Magazine instantly reloads everything, Rapid Spark stops bullets being consumed for 2 seconds, and Windmill Killer completes reloading twice.
• Buff windows: Flash Frost gives Fire Rate and Reload Speed +50% and doubles its own passive for 3 seconds. Mega Meteor gives Bullet Size and Bullet Attack +50% for 3 seconds.
• Guaranteed rolls: Spread makes your next shot always deal both a Smite and a Critical Hit.
• Status setup: Snow King freezes after a two second wind up, and Calamity Blaze burns every enemy currently under a Transmutation.

If your run keeps failing because you get caught reloading, a reload Battle Skill is worth more than a bigger number. If it fails because elites survive, take the damage active.

Battle Skill Damage is its own damage channel

Most part actives deal Battle Skill Damage, which is a separate category from Bullet Damage and Transmutation Damage. Relics that boost Battle Skill Damage boost these actives, and 66 relic entries in the current build mention it. Forged Iron’s passive is simply Battle Skill Damage +30%.

That matters when you compare a 300-damage active against a weapon shot: they scale from different sources, so a build stacked toward bullets makes its Battle Skill relatively weaker and vice versa.

Passives come in three shapes

The simplest are flat element lines: Lightning Shooter, Deep Winter, and Soul Shock each give +15% of their element at Common. They are predictable and they never fail to apply.

The second group is conditional and usually stronger. Chaos Fire gives +2 Projectiles on Final Shot. Volley adds +30% damage to both First Shot and Final Shot. Bulwark Breaker gives +20% Critical Chance on a full charge. Filament Split has a 25% Adaptive Chance while shooting to grant +4 Projectiles, which follows the Adaptive Chance rules rather than a flat roll.

The third group changes your rhythm. Rapid Spark auto-reloads a bullet every 4 shots. Heavy Magazine builds Rapid Fire stacks that all disappear when you reload, which pushes you to empty the magazine. Corrosion Scar fires a Scorpion Stinger every 0.2 seconds while you reload, which makes reloading an attack instead of downtime.

Match that third group to your weapon’s magazine and cadence. A 20-round weapon and a 1-round charge weapon want opposite parts.

Rarity variants and the four self-upgrading parts

Thirty six parts exist at Common, Rare, Epic, and Legendary, so the same part can appear at four power levels. Two parts appear only at Epic and Legendary, and seven are Mythic only, including Havoc, Annihilation, Calamity, Gluttony, Crimson Lotus, Windmill Killer, and Heart of Termination.

Four parts are unusual: they are named after rarities and upgrade themselves through kills. The Common one upgrades to Rare after 25 kills, Rare to Epic after 50, and Epic to Legendary after 100. The final Legendary stage grants a permanent +1% Physical Damage for every enemy killed while it is installed. Taking that chain early is an investment; taking it late is close to worthless.

Mythic parts are worth a separate mention because they change the weapon rather than improving it. Heart of Termination stops your weapon firing regular bullets at all and replaces them with piercing Sword Force Waves at 666% Bullet Attack. Read a Mythic part as a new build, not an upgrade.

Your sub weapon’s part is not doing anything

Two tarot cards make this explicit. The Lovers grants you the weapon effects of your sub weapon and the passive effects of your sub weapon part. The Lovers (Reversed) makes your Battle Skill also cast the sub weapon’s Battle Skill.

Read that as confirmation that by default only the installed part on the weapon you are holding is working. Planning a second part as if both passives stack is the most common way a loadout looks stronger on paper than it is in the room. If you want both, the cards are on the Tarot database.

Choosing at the Forge

Ask three questions in order. Which failure keeps ending your runs, and is there an active that solves it? Does the passive condition match how this specific weapon fires, or is it asking for a Final Shot on a 20-round magazine? And is your relic set pushing Bullet Damage or Battle Skill Damage, because that decides how much the active is really worth.

When two parts look close, prefer the one whose condition your weapon meets automatically. Compare the finished pairing, weapon plus part plus relics, in the Build Planner instead of trusting the largest printed number.