Lynel of Ploymus Mountain
The mountain was the territory of a Lynel since before the Great Calamity as one terroried Zora's Domain in the past according to two weathered Zora Stone Monuments and Mipha's Diary only to be defeated by the Knight and Hero Chosen by the Master Sword Link. Mipha's Diary reveals the full story of how Princess Mipha told Link of the Lynel causing him to travel to Ploymus Mountain to slay the beast. Mipha secretly followed Link who upon discovering her told her to return to Zora's Domain but she stubbornly refused. Suddenly the Lynel attacked them though Link easily defeated it with his sword skills, finishing it off with a Spin Attack. Link was hailed as a hero for defeating it and the Zora Helm was placed in a small shrine at Toto Lake in rememberence.
One hundred years later, Link finds a Lynel living on the mountain (it is unclear if the one Link defeated previously was resurrected by Calamity Ganon or if it is a descendant of the Lynel that Link slayed in the past). This Lynel is not replaced by stronger Lynels as Link progresses through the game and is resurrected after every Blood Moon. During the Side Quest "Lynel Safari", Laflat asks Link to take a picture of a Red-Maned Lynel like the one on Ploymus Mountain to with the Camera Rune and will reward him with the Zora Greaves after showing it to her. She requests the picture so she can scare Zora away from Ploymus Mountain to prevent Zora from getting hurt from diving off Shatterback Point into the East Reservoir Lake.
The Red-Maned Lynel on Ploymus Mountain is the only Red-Maned Lynel in Master Mode as a picture of one is necessary to complete "Lynel Safari" thus it never levels up to a stronger variant even in Master Mode.