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Because Viktor is a controlling bastard. He manipulates and controls people by manipulating and controlling information. Same way he lies to Selena to keep her under his control, same way he had lied and manipulated Marcus, same way he kills Selene's family as well. In Evolution, we learn that Viktor banished Tanis due to the history Tanis was recording. We know its factual, but with Tanis gone, Viktor can change history.

Selene: Andreas Tanis. He was the official historian of the Covens. He fell from favor after documenting what Viktor considered "malicious lies". Of course, as it turns out, he was probably telling the truth.

Very few immortals in the modern day are old enough to know the truth. Viktor, Kraven, Tanis, Marcus (arguably William as well), Lucian, Raze, and Amelia, the warrior turned princess who is killed on the train. All the other vampires died in Rise of the Lycans when the werewolves and Lycans overran the castle.

Keep in mind that even the events of Rise of the Lycans happen well well after Viktor becomes a Vampire and the 3 elders have started leapfrogging through time. The production notes and websites in Evolution note that Viktor was 1400 years old, and Rise of the Lycan he was 1000 years old. William wasn't captured until 1202 AD.

He likely still believes that killing Marcus could in turn kill him, a bluff that Marcus used to keep himself and William alive even though Viktor commanded the loyalty of an army. Having someone look into the legend could have problems for Viktor (Death, Freeing William, Hybrids or Worse), which he very much does not want.

Because Viktor is a controlling bastard. He manipulates and controls people by manipulating and controlling information. Same way he lies to Selena to keep her under his control, same way he had lied and manipulated Marcus, same way he kills Selene's family, same way he even lied to Lucian as well. In Evolution, we learn that Viktor banished Tanis due to the history Tanis was recording. We know its factual, but with Tanis gone, Viktor can change history.

Selene: Andreas Tanis. He was the official historian of the Covens. He fell from favor after documenting what Viktor considered "malicious lies". Of course, as it turns out, he was probably telling the truth.

Very few immortals in the modern day are old enough to know the truth. Viktor, Kraven, Tanis, Marcus (arguably William as well), Lucian, Raze, and Amelia, the warrior turned princess who is killed on the train. All the other vampires died in Rise of the Lycans when the werewolves and Lycans overran the castle.

Keep in mind that even the events of Rise of the Lycans happen well well after Viktor becomes a Vampire and the 3 elders have started leapfrogging through time. The production notes and websites in Evolution note that Viktor was 1400 years old, and Rise of the Lycan he was 1000 years old. William wasn't captured until 1202 AD.

He likely still believes that killing Marcus could in turn kill him, a bluff that Marcus used to keep himself and William alive even though Viktor commanded the loyalty of an army. Having someone look into the legend could have problems for Viktor (Death, Freeing William, Hybrids or Worse), which he very much does not want.

Aside from Viktor's overall characterization and actions, there's the out-of-universe reason. Many things in Underworld are essentially retconned when the movie got sequels. A straight forward hidden mythology of Vamp vs Weres was stamped over when they had to give details to expand the series with sequels and prequels. Just like Blonde Sonja. The original expanded history of Underworld was shown in Blood Enemies, a now non-canon prequel novel to the movie before Evolution or Rise were conceived.

Because Viktor is a controlling bastard. He manipulates and controls people by manipulating and controlling information. Same way he lies to Selena to keep her under his control, same way he had lied and manipulated Marcus as well. In Evolution, we learn that Viktor banished Tanis due to the history Tanis was recording. We know its factual, but with Tanis gone, Viktor can change history.

Selene: Andreas Tanis. He was the official historian of the Covens. He fell from favor after documenting what Viktor considered "malicious lies". Of course, as it turns out, he was probably telling the truth.

Very few immortals in the modern day are old enough to know the truth. Viktor, Kraven, Tanis, Marcus (arguably William as well), Lucian, Raze, and Amelia, the warrior turned princess who is killed on the train.

Keep in mind that even the events of Rise of the Lycans happen well well after Viktor becomes a Vampire and the 3 elders have started leapfrogging through time. The production notes and websites in Evolution note that Viktor was 1400 years old, and Rise of the Lycan he was 1000 years old. William wasn't captured until 1202 AD.

He likely still believes that killing Marcus could in turn kill him, a bluff that Marcus used to keep himself and William alive even though Viktor commanded the loyalty of an army. Having someone look into the legend could have problems for Viktor (Death, Freeing William, Hybrids or Worse), which he very much does not want.

Because Viktor is a controlling bastard. He manipulates and controls people by manipulating and controlling information. Same way he lies to Selena to keep her under his control, same way he had lied and manipulated Marcus, same way he kills Selene's family as well. In Evolution, we learn that Viktor banished Tanis due to the history Tanis was recording. We know its factual, but with Tanis gone, Viktor can change history.

Selene: Andreas Tanis. He was the official historian of the Covens. He fell from favor after documenting what Viktor considered "malicious lies". Of course, as it turns out, he was probably telling the truth.

Very few immortals in the modern day are old enough to know the truth. Viktor, Kraven, Tanis, Marcus (arguably William as well), Lucian, Raze, and Amelia, the warrior turned princess who is killed on the train. All the other vampires died in Rise of the Lycans when the werewolves and Lycans overran the castle.

Keep in mind that even the events of Rise of the Lycans happen well well after Viktor becomes a Vampire and the 3 elders have started leapfrogging through time. The production notes and websites in Evolution note that Viktor was 1400 years old, and Rise of the Lycan he was 1000 years old. William wasn't captured until 1202 AD.

He likely still believes that killing Marcus could in turn kill him, a bluff that Marcus used to keep himself and William alive even though Viktor commanded the loyalty of an army. Having someone look into the legend could have problems for Viktor (Death, Freeing William, Hybrids or Worse), which he very much does not want.

Because Viktor is a controlling bastard. He manipulates and controls people by manipulating and controlling information. Same way he lies to Selena to keep her under his control, same way he had lied and manipulated Marcus as well. In Evolution, we learn that Viktor banished Tanis due to the history Tanis was recording. We know its factual, but with Tanis gone, Viktor can change history.

Selene: Andreas Tanis. He was the official historian of the Covens. He fell from favor after documenting what Viktor considered "malicious lies". Of course, as it turns out, he was probably telling the truth.

Very few immortals in the modern day are old enough to know the truth. Viktor, Kraven, Tanis, Marcus (arguably William as well), Lucian, Raze, and Amelia, the warrior turned princess who is killed on the train.

Keep in mind that even the events of Rise of the Lycans happen well well after Viktor becomes a Vampire and the 3 elders have started leapfrogging through time.

He likely still believes that killing Marcus could in turn kill him, a bluff that Marcus used to keep himself and William alive. Having someone look into the legend could have problems for Viktor, which he very much does not want.

Because Viktor is a controlling bastard. He manipulates and controls people by manipulating and controlling information. Same way he lies to Selena to keep her under his control, same way he had lied and manipulated Marcus as well. In Evolution, we learn that Viktor banished Tanis due to the history Tanis was recording. We know its factual, but with Tanis gone, Viktor can change history.

Selene: Andreas Tanis. He was the official historian of the Covens. He fell from favor after documenting what Viktor considered "malicious lies". Of course, as it turns out, he was probably telling the truth.

Very few immortals in the modern day are old enough to know the truth. Viktor, Kraven, Tanis, Marcus (arguably William as well), Lucian, Raze, and Amelia, the warrior turned princess who is killed on the train.

Keep in mind that even the events of Rise of the Lycans happen well well after Viktor becomes a Vampire and the 3 elders have started leapfrogging through time. The production notes and websites in Evolution note that Viktor was 1400 years old, and Rise of the Lycan he was 1000 years old. William wasn't captured until 1202 AD.

He likely still believes that killing Marcus could in turn kill him, a bluff that Marcus used to keep himself and William alive even though Viktor commanded the loyalty of an army. Having someone look into the legend could have problems for Viktor (Death, Freeing William, Hybrids or Worse), which he very much does not want.