While Warner Bros and Monolith Productions managed to score a hit with fans and critics alike with Middle-earth: Shadow of Mordor and its sequel, which pits players in the role of the Gondorian ranger captain Talion between the events of The Hobbit and The Lord of the Rings. After the Gondorians living at the Black Gate were wiped out, Talion is seemingly revived by the wraith known as Celebrimbor and the duo storm into Mordor to exact revenge. However, the real standout feature for many was the Nemesis System.
Through this feature, the artificial intelligence for NPC enemies in Shadow of Mordor was able to learn from the player and their actions. Essentially, any Uruk the player battles is tracked by the game highlighting those who survive or even manage to kill the player. From there, they grow stronger from it, getting promoted higher in the ranks, and more difficult to kill. Uruks that are killed by the players could also return, remembering the player's prior actions and changed based on how the player took them out previously. In addition, they may recall the previous battle, taunting the player of their return and additional traits gained from the battle.
This ability to personalize and dynamically alter the game made most fans believe the Nemesis System would be copied and utilized in plenty of other games in the future. While that may not have happened on a large scale, the reasoning may be due to Warner Bros attempting to file a patent for it all the way back in 2015. Specifically, the patent was filed for "Nemesis characters, nemesis forts, social vendettas and followers in computer games" though considering more recent games like XCOM 2: War of the Chosen utilize a similar mechanic, the patent has yet to leave the pending state.
Since its filing in 2015, the patent has had a lot of activity including being rejected a couple of years ago. However, Warner Bros refiled and the patent was re-examined as early as 2020, which then was placed into the notice of allowance stage. This indicates that if the paperwork and fees are filed by Warner Bros in a certain amount of time, the final patent will be issued.
It is worth noting that even if Warner Bros manages to get the patent for the Nemesis System, it does not prevent similar mechanics from being developed and used. There are countless of examples of companies owning a patent on traditional game mechanics, such as Microsoft owning a patent on games that award bonus points for players that perform feats of style, Nintendo's patent on a sanity mechanics from Eternal Darkness, or Electronic Art's 2006 patent on BioWare's dialogue wheel, one of the most used mechanics in any RPG style game. In fact, Bloober Team just recently filed a patent for The Medium's gameplay mechanic that lets players simultaneously play in two different environments at the same time.
Source: Game Maker's Toolkit; PC Gamer; Google Patents