The Goblin King really depends on which fantasy realm you're walking into, but I've always felt the most iconic version is Jareth from 'Labyrinth'. Sure, it was a movie first, but the character's influence on novels is undeniable—you can see his theatrical, glam-rock swagger echoed in so many modern fae and goblin monarchs. For a more traditional, Tolkien-esque feel, the Goblin King in 'The Hobbit' is a classic archetype of the monstrous underground ruler, though he's less a character and more a force of nature.
Then you've got the recent surge in romance and romantasy that's completely reimagined the trope. Authors like Katee Robert or K.F. Breene write goblin kings who are fiercely possessive, politically cunning, and often shockingly charismatic love interests. It's a shift from pure villain to morally grey, complex ruler, sometimes even the protagonist. This version leans into the 'otherness' and raw power that can be so compelling in paranormal romance.
Honestly, my personal favorite is the Goblin King from Emily Tesh's 'Silver in the Wood' novella sequel, 'Drowned Country'. He's melancholy, bound to his forest, and represents a wild, ancient magic that's fading from the world. It's less about grandeur and more about a deep, sorrowful connection to a place. That version stuck with me long after I finished reading.