The flutter in the vortex got worse.

  Over the next three days, as Chen Xi trained for the tournament and deepened his analysis of the Arena's formation structure, the interaction effect with Li Wei's energy field intensified.

  He tracked it obsessively.

  The data was clear: when Li Wei was within approximately thirty metres, Chen Xi's vortex drew ambient Qi at an accelerated rate.

  The acceleration was not large — perhaps seven percent above baseline — but it was consistent and directional.

  His vortex was pulling energy from Li Wei's vicinity.

  He ran the fluid dynamics. The mathematics were uncomfortable.

  The vortex operated by creating a low-pressure zone.

  Low-pressure zones draw from surrounding high-pressure areas.

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  This was fundamental — it was why the vortex worked at all, pulling ambient Qi from the environment.

  But in an environment with other cultivators, the "environment" included their personal energy fields.

  His vortex was not distinguishing between ambient Qi and Qi that was being actively circulated by another person's cultivation.

  It was siphoning both.

  The effect was proportional to proximity and the target's cultivation level.

  Against mortals: undetectable. Against low-level cultivators: negligible.

  Against someone at Li Wei's level — Foundation Peak, strong and stable — seven percent.

  Against someone stronger: potentially much more.

  He had built a parasite.

  Chen Xi stared at his calculations and felt, for the first time in this world, something he recognised from his previous life: the cold, specific dread of a scientist who has discovered that their work has an unintended consequence.

  The Vortex Core was not just a cultivation method. It was an energy extraction system that, in sufficiently dense cultivator populations, would drain everyone around him.

  Slowly. Silently. Without his knowledge or consent.

  He had been doing this to Wu Zheng for six weeks.

  The old man's cultivation recovery — which had been slower than expected, which Wu Zheng had attributed to decades of damage — had been hampered by Chen Xi's presence.

  He had been stealing from his only friend.

  He closed his notebook and went to find Wu Zheng.