Soul Debt

In the Underdark's primordial era, when the first mercenaries discovered they could strip relics from rivals, a dark entity that lurks in the deepest caverns cursed all future transactions with binding obligation. No tag transfer comes without cost. The Soul Debt was born from this ancient bargain - take a relic, and a piece of your essence remains in the depths, waiting to be repaid.

The Soul Debt manifests as two small orbs connected by a spectral chain - one orb pulses with neon green luminescence while the other absorbs all light around it. The chain's tension physically reflects the holder's debt status: loose when debt is low, uncomfortably tight when debt accumulates. The artifact weighs differently depending on the holder's karmic balance, and it vibrates with increasing intensity when near delvers who hold opposing debt.

This relic serves as the Underdark's karmic accounting system. Every tag exchange modifies the holder's debt level, which then applies modifiers to future raid attempts - high debt imposes penalties while low debt grants bonuses. The Soul Debt creates a perpetual balance where aggressive delvers must eventually 'pay' for their conquests through reduced effectiveness, while defensive players who honor challenges are rewarded.