These are the relationships of the Dark Lord, the Overlord.
Pythor brought the Overlord back online to help him get the Golden Power to become the Golden Master. The Overlord was shocked at Pythor restoring him, though he gained a liking for Pythor after he saw how vile and cunning he was and both worked to capture Lloyd.
The Overlord started to show respect to Pythor, going as far as to include Pythor as an ally during the attempted Golden Master apocalypse. Pythor respected him in return, protecting him from the Ninjas' attack and ended up being shrunk.
First Spinjitzu Master (Arch Nemesis)
The Overlord acted as the First Spinjitzu Master's dark counterpart to counterbalance of the Balance between light and shadow. The Overlord and the First Spinjitzu Master waged war on each other and battled for decades, each of them evenly matched and neither able to defeat the other and gain the upper hand, until the Overlord created the Stone Army to help him turn the tide in his favor. The First Spinjitzu Master did what he could, but he knew he would soon be defeated, so he divided Ninjago in two.
The Overlord met Garmadon after the latter washed up in the Dark Island. He aided the villain for his plans to rule Ninjago. But in reality, the dark villain used the four-armed villain to upset the balance so that he can be free and rule Ninjago in his image. The Overlord possessed Garmadon in his attempt to conquer Ninjago.
After he was defeated, The Overlord unintentionally cleansed Garmadon of all the evil plaguing him for centuries.
Lloyd Garmadon is the grandson of his arch enemy, the First Spinjitzu Master, and his new arch-enemy. Lloyd defeated him in the Final Battle. He later tried to steal Lloyd's Golden powers to become the Golden Master.