in solstheim in a mountain discover a dead body surronded of candle that is evident that was a dark brotherhood ritual theyre but i dont start the dark brotherhood quest with my xbox character so im not affiliate to them yet. so i wanna know if this thing have a purpose link with a dark brotherhood quest or its just theyre for fun?

I'm 99.9% sure that there is no Brotherhood presence on Solstheim.

its not what i write . they have a ritual been made theyre. so the logic thing its someone from solstheim make a ritual. so we answer that person call if we are in the dark brotherhood or its just theyre for fun?

If you are talking about the sacrifice on the altar of Thrond then no.
Also Dunmer generally dont use the 'illegal' dark brotherhood when the same can be achieved with the perfectly legal Morag Tong.

no its not theyre its like in the middle of nowhere you climb n then you see that in a corner of rock.