So, one characteristic of Xie Lian having his curse mark is that he has the shittiest luck ever. Literally think if there is a pebble on the road he will stumble on it. It seems like a good time for that to come into play.

Another interesting thing is that he literally cannot die, so that will be interesting.

TROUBLE AT SEA

Open to Xie Lian fumbling/losing his candle, if someone wants to be in the boat with him. OTOH, he can definitely punch mermaids/zombies, so....

ELLETHIA

So, because of his shit luck, Xie Lian's suit will get ripped, and because he literally doesn't feel pain or rather, he's become so used to it it barely registers, he won't realize until it's too late. So if someone wants to alert Xie Lian that his arm or leg is rotting, that would be really nice. And also witness the slight trauma reaction and/or seeming indifference to the situation.

THE SILENCE GAME

Again, shit luck means he's probably going to stumble on something and alert mermaids at least once. He probably won't need much rescue but people can come help anyway.

ELLETHIA-HAMSOUR/LIGHTHOUSE
Xie Lian won't feel the compulsion so if you need someone to tie your character up/holds them back, he's your... god? I guess?