Soul Hunter Crossbow (unique Burst Crossbow), Moon Daggers (unique Daggers), and Soul Fists (unique Gauntlets) do not access to soul weapon exclusive enchantments, despite the fact they have the +1 soul collection attribute. The following enchantments cannot be applied to the following items:

Soul Fists, Moon Daggers, Soul Hunter Crossbow:

• Anima Conduit
• Soul Siphon

The only soul enchant the weapons have access to is Enigma Resonator, but that is only because it is the unique built in for these weapons. The game only sees them as Daggers, Gauntlets, and a Burst Crossbow with ER, not proper soul weapons.