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The game has the chance of presenting an enemy orc leader with the nickname 'King-Slayer' and one missing hand. This is a reference to Jaime Lannister from 'A Song of Ice and Fire'/'Game of Thrones.Jaime killed the 'The Mad King' Aerys II Targaryen he was sworn to protect and lost his hand from Locke.
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Talion's dagger, Acharn, is his son's broken sword, and bears a strong resemblance to Narsil, the powerful sword wielded by King Elendil in the Lord of the Rings universe. Acharn means Vengeance in the Elven language Sindarin.
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The Morgul Bat's entry in the Appendices menu reads, "Those Uruks that get poisoned become horribly diseased and bloated, wearing their deformities as marks of honor. The poison slowly eats at their minds, sending them nightmares of a demonic man-bat who preys on fear."

This is a reference to Batman, most likely because of the Batman: Arkham series, also published by Warner Bros.