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). He first appears in a meeting with Deckard, where claiming that he wishes to see a negative result before he gives Deckard a replicant to test he demand that Deckard use the Voight Kampff test on his assistant Rachael, only for Deckard to discover that Rachael is in fact a replicant, specifically one with memory implants taken from his niece's memory thus making her harder to detect as a replicant. He plans to use this in all replicants, believing the memories will provide a "cushion" for the replicant's emotional development and subsequently make them easier to control. Late he is shown to playing long distance chess with J.F. Sebastian, something Roy Batty exploits to get Tyrell to allow Sebastian to enter his living quarters, unaware that Batty is there too. Tyrell remains calm and explains that altering DNA is fatal in all circumstances. He attempts to comfort Roy referring to him as the prodigal son and reminding him "The light that burns twice as bright burns half as long." This does little to comfort Batty who kisses Tyrell and then proceeds to crush his skill in, killing him as a horrified Sebastian looks on. His body along with Sebastian's is found by the police shortly after.
He refers to Replicant's as his children, part of his metaphorical comparison to God, as he demonstrates the power to create life, block the light of the sun as he wishes it, displays vast knowledge and lives in a vast golden place, where he is supreme ruler. Batty is his Lucifer, his most perfect creation rising up to challenge and then seeking to destroy his creator. Indeed all rogue replicants are presented as like fallen angels, faster, stronger and on the whole more intelligent beings than humans who can nevertheless walk amoung them, turning from the "Wisdom" of their creator and rising up against led by the greatest of them. He is also a master chess player, losing to fellow master J.F Sebastian only twice, and the second time, he lost because Batty told Sebastian what moves to make. He also possesses a pet owl, used as a symbol of wisdom, however as the Owl is artifical is can be seen as showing that Tyrell has "False wisdom".
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 him. 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.