A series of weapons based on the Apocrean ability to steal souls.
Sword = "Power"
Normal hits = like a faster, larger brandish that does zero damage but knocks many souls out of enemies.
Charge = destroy all of the souls you've collected, dealing heavy damage to all enemies that have had their soul taken. As a side effect, the sword deals an area of effect around it that deals damage based on the number of souls stolen. If very few souls are stolen, this side effect is almost meaningless.
Gun = "Vision"
Normal hits = like argent peacemaker, but invisible and 3 at a time, spread similar to a shotgun. Each bullet steals souls. No need to reload.
Charge = destroy all souls collected, just like the sword's charge. Grants an attack+speed+defense orb to team mates and the user based on number of souls stolen.
Bomb = "Patience"
Charge = Create a circle on the ground similar to the Apocrean beam. Enemies in this beam-like area have their souls freed.
Each time the bomb is dropped, it destroys souls with its radius increasing from being the size of a 3* vortex bomb to being larger than most 5* bomb radii. This bonus would reset every time a bomb is dropped.
The soul mechanic
Souls travel into the nearest soul stealing weapon. So if I shoot enemies rapidly while the bomber is running around spamming Dexterity and that bomber is closer, their weapon will absorb the souls instead of mine. If no soul weapons are present (e.g. I drop my bomb and switch weapons), the souls fly back into the enemy and no damage is dealt.
All damage dealt is normal, and very high since the knight is going through a lot of trouble to use soul weapons. Optionally, destroying souls could cause fire to that enemy.
Switching weapons releases all of the souls, which then attempt to find a new home, be it a different knight or back into the enemy. This would allow knights to stack all of the souls onto one person, should they choose.
The different weapons would knock out different numbers of souls at different rates, where the bomb would have the highest damage, the sword would have the highest burst damage, and the gun would simply be the most mobile. The rate of damage would be almost double what their regular variants would do, with the bomb being comparable to dark retribution (but neutral to all instead of limited to shadow).
Obsidian weapons would also be able to capture souls, and would grant the user with a small defense orb, based on the health of the souls held. Attacking with the obsidian weapon would damage the souls they obtained with each hit until they were gone, at which point their defense orb would be removed and that enemy would have taken much damage. Hitting enemies with obsidian weapons would not release souls as would hitting enemies with the new weapons described above.
I think this would be cool too.
But if the soul.destroying part means you have to pay all the souls you found. I would cut that off.
I would also cut out the switch weapon-release souls effect.
Aside from the above things i said. It's a really cool idea