Cull's Shadow

• Soulburn: final blows or rapid hits with the frontal blades heal you and give Soulfire Charges, which make the rounds inflict potent corruption. The blades deal more damage to corrupted targets.
• Blades of Unmaking: a melee with the blades, a swift two-hit combo.
• Soulforge: corrupted targets turn into soulfire crystals when defeated, and the crystals detonate when destroyed.
• Catalyst refits: Soulfire Succor (reload and charges from blade hits on crystals), Soulfire Rancor (crystals expel corruption and detonate on their own), Soulfire Zeal (damage resistance and speed from nearby detonations) and Soulfire Skewer (blades inflict corruption).

The Oblation exotic mission is split into Bloodline, Soulfed and Immolation, and Bungie's record for the rifle says it is acquired from Oblation. Bloodline is the first part; the later parts pay out the Soulfire Rancor and Soulfire Skewer refits in the activity data. A hands-on guide credits the Bloodline boss fight with the weapon and ties the Succor catalyst to a Hive grimoire and rune-door puzzle in the boss room.

• Options: Obtain Cull's Shadow, Only the Catalysts, or Weapon + All Catalysts.
• Catalysts: Soulfire Succor, Rancor, Zeal and Skewer, either added to the weapon or on their own. Extras: Self-play (Sherpa).

• The Oblation exotic mission, added in Update 9.7.0, which starts by helping Aunor Mahal recover a Weapon of Sorrow.
• Exotic missions are Pinnacle Ops for up to three players; some depend on an expansion, so the manager checks yours.

Which part of Oblation gives the rifle?

The first part, Oblation: Bloodline, which ends with the boss Valus Tau'Rig, The Insatiable.

Is the weapon Kinetic or an energy weapon?

Kinetic, and it uses Special ammo.