Records of the Three Kingdoms
Dian Wei was from Jiwu in Chenliu. He was large and powerful, and Cao Cao took him as a close guard. The histories stress that post, not a tournament at the start of his service.
In 197 Cao Cao campaigned against Zhang Xiu. Zhang Xiu surrendered and then rebelled. Dian Wei held the camp gate. Those around him were nearly all dead or wounded. He himself took dozens of wounds and still fought, and at last was killed. Cao Cao got away. Whenever Cao Cao later passed the Wan area he sacrificed to Dian Wei. Dian Wei did not live to see Guandu or Red Cliffs.
Romance of the Three Kingdoms
The novel gives him a pair of halberds and, at Wan, has him fight on after he has been drinking, until he dies in the rout. Cao Cao weeping at the sacrifice comes back more than once.
To put him still at Cao Cao’s side at Red Cliffs would be a mistake of time. The novel’s main line does not make it.
Reference: Wikipedia · Dian Wei