Dr. Eldon Tyrell is a genius who has built up the large Tyrell Corporation. His creations are Replicants. Some of them are given away "free" to people accepting the offer to emigrate to the Off-World colonies. Others are used in combat to protect those settlers, (from what, we don't know). Roy Batty, lead by J.F. Sebastian, finds Tyrell and kills him by crushing his skull.
It was originally intended that the Tyrell murdered by Batty would be revealed to be a replicant, and as a result Batty would head up to the next floor, where he would discover the real Tyrell in cryogenic suspension. Sebastian would then explain that a uncurable disease struck Tyrell, who had himself frozen until a cure is found. Subsequently Batty would demand that Sebastian awaken Two different versions exist on what would have happened next, in the 1st, Sebastian would brake down and admit that he made an error years earlier and resulted in Tyrell's death and in a rage, Batty kills him. In the 2nd Sebastian reveals that years before (estimated as 2013) a blackout struck the city, and during the approximately 45 minutes the power was out, Tyrell's life support failed and he died. Again Batty is struck by despair and feeling there is no hope, he kills Sebastian much as he did in the finished film
In the Blade Runner video game, it is shown that Tyrell met with rookie Blade Runner Ray McCoy shortly after meeting with Deckard and spoke briefly with him about the death of one of his senior Gravity Lab technicians, but he provides little useful information. It also reveals that just hours before his death at Batty's hands he had narrowly survived a confrontation with a Nexus 6 named Clovis who unlike Batty, does not ask for more life from Tyrell himself, but rather for the DNA data on the Nexus 6 in the hope of using it to find a way to prolong his lifespan himself without Tyrell's involvement. When Tyrell insists the 4 year lifespan is unalterable, Clovis moves to shoot him, but is thwarted by Tyrell's security team. Tyrell is also revealed to be attempting to convince Governor Kolvig to allow replicants to work on Earth, but the governor is killed by Clovis not long after this proposal is made.