These boots are the magic equivalent of Bandos boots and Armadyl boots. Being Power armour, they offer a Magic bonus. Thereby they give highest non-degradeable Magic bonus available for boots in the game. They are part of the Robes of Subjugation set.
Not long after Zamorak achieved godhood, he became worried about his followers, whom were not loyal to him and were planning to betray him the same way he did with Zaros. Seeing that, he visited Razulei in the Infernal Dimensions and requested the creation of the robes of subjugation, powerful robes imbued with cruelty. After they were created, Zamorak paid Razulei handsomely and gave them to his mages. His mages drew power from the clothes with the objective of overcoming him and were flooded with pain. Desperate to cease it, they drew even more power from the robes, but it only worsened the pain and it eventually killed them.
After Zamorak's banishment, his followers that wished to return him to Gielinor were loyal, so they could use the power of the robes without succumbing to pain, but prospering in the name of Zamorak.
Despite its name being 'boots' of subjugation, they are simply spiked ankle bands and strips of material that cover the metatarsal bones of the player's feet, closer to sandals than boots.
The boots rapidly dropped in price when the Evolution of Combat was released, since they no longer offered a 1% magic damage boost, and ganodermic boots were a cheaper and superior alternative to people with 75 Defence.