Yes, Gold Lynels exist in The Legend of Zelda: Breath of the Wild, but only in Master Mode, as the strongest tier of enemy, appearing after significant in-game progress where you've defeated many other enemy types. They are exceptionally powerful and drop rare materials, making them a significant challenge and goal for players in the game's hardest difficulty.
Golden Lynels are the strongest type of Lynel exclusive to Master Mode in Breath of the Wild. According to the Hyrule Compendium, Golden Lynels are said to have been Silver Lynels that were mysteriously transformed once they were struck by Lightning, consequently increasing their offensive power and overall health.
Enemies give you EXP for killing them up to 10 times. After you crossed certain EXP thresholds the Lynels will scale up. First to blue ones, then white, then silver and lastly gold. If you just play normally and defeat a wide range of different enemies, you will unlock them normally at some point.
A Gold Lynel has 7,500 HP. The strongest enemy attack in the game is a swing from a Gold Lynel with a Savage Crusher that has +30 attack up. Lynel deals 60 damage.
Gold Lynels are strongest tier of Lynels and they only appear in Master Mode. Master Mode just added an extra tier of enemies.
Blue-Maned Lynels (HCN 148) are one step up from Red. White-Maned Lynels (HCN 149) are even more difficult to beat and fairly rare. Silver Lynels (HCN 150) are the most difficult to defeat and the rarest.
They have been influenced by Ganon's fiendish magic, so they are the strongest among the Lynel species, surpassing even the strength of those with white manes. The term "silver" denotes not only their color but also their rarity. The purple stripes help them to stand out even more.
Staying in a Lynel's territory for too long is considered an act of aggression, which makes sense, so naturally it's eventually going to retaliate.
In Master Mode in Breath of the Wild, Golden Bokoblins, Golden Moblins, Golden Lizalfos, and Golden Lynels appear as a stronger variant than silver enemies. According to the Hyrule Compendium, Golden Monsters are silver enemies that underwent a mysterious transformation after being struck by lightning.
Considering these Lynels are found in the Dark World, they were created by Ganon himself to be part of his army when invading the Light World.
The Hyrule Compendium says that the Common Locations of Silver Lynels are "Unknown." This is because they don't start appearing until the world has been scaled up significantly. If you're still seeing Red, Blue, or White Lynels, keep defeating various enemies to advance the invisible scaling system in TotK.
The mask is much more difficult to get in Tears of the Kingdom than it was in its predecessor, Breath of the Wild, since you must defeat a whopping five Lynels in a row at the Floating Coliseum. This challenge may be one of the hardest in Hyrule, and requires a lot of preparation.
Black Lynels appear only in the Treacherous Tower in A Link Between Worlds, on the 49th floor of the Advanced level. They have the same amount of health and deal the same damage as regular Lynels, but have the ability to spit single fireballs in addition to breathing streams of fire.
They view combat as a sacred act, and may ritually consume parts of difficult opponents in order to assume their best qualities. Lynels are not inherently evil, but they do respect shows of force, and can be persuaded to follow evil masters that are sufficiently domineering.
Breath of the Wild
Lynel Guts are Monster Parts that can be dropped by all types of Lynels upon their defeats. They pulse with the vitality of a Lynel, which makes them useful for making Elixirs in a Cooking Pot.
The rarest items in Breath of the Wild are subjective but often include rare materials like Smotherwing Butterflies, Big Hearty Truffles/Radishes, Star Fragments, Giant Ancient Cores, and specific unique weapons like the Hylian Shield or certain event-exclusive gear; however, the truly rarest is the Glitched Ice Cream, a placeholder item that's incredibly hard to get through specific glitches.
Blood Moons most commonly appear once every 2-3 hours of continuous gameplay and, under normal circumstances, will trigger at midnight in-game. However, in situations where the game is running out of memory or assets are not loading correctly, a "Panic" Blood Moon will be triggered, even during daytime.
majora's mask works on lynels the same way the lynel mask does. Which is to say, it delays aggro for a bit, but not permanently.
Nope, Lynels are totally immune to all elemental effects.
Breath of the Wild
Savage Lynel Swords are used by White-Maned Lynels, Silver Lynels, and Golden Lynels. As it takes time for Lynels to scale up, Savage Lynel Swords may not be available until later in the game.
Summary: Gold Lynels are twice as likely as Silver Lynels to drop Diamonds or Star Fragments. Gold Lynels have a 25% to drop at least one Diamond and a 25% chance to drop at least one Star Fragment, considered separately; compared to a 1-in-8 chance for Silver Lynels.
Regular Lynels predominately use Lynel Shields, however Blue-Maned Lynels in Master Mode will use them instead. They can become scarce as Lynels tier up, but since the Lynel on Ploymus Mountain will always remain a regular Lynel, it will always be a source of Lynel Shields.