Don't sacrifice yourself either

Xi Zirui stays silent during the qi transfer. He focuses on opening his meridians and letting the qi flow from his body into Han Yu's -- making him stronger, helping him fight the poison cursing through him.

The downside is that the more Xi Zirui transfers, the weaker he grows. It's harder and harder to keep his mind clear the longer the transference goes on. 

His mind grows sluggish and heavy -- losing qi is not unlike losing blood. Except to a cultivator it's perhaps even more vital. 

Your qi can help you replenish blood loss, but the only thing that can replenish depleted qi is meditation and the interaction with the natural world. 

Depending on how much qi is lost, that can be a long process.

If all qi is exhausted, it can be fatal.

Xi Zirui senses the world growing dark around the edges, dimmer with each passing second.

He's faintly aware of Han Yu's voice sounding very faint, as if coming from a great distance.