Kings of Chaos
Eight of the nine aligned planes have a single lord to rule over them. The chaotic neutral plane is the only exception, and has two: the self-proclaimed Kings of Chaos. They rose to power only one hundred and fifty years ago, and even with their combined might are considered the weakest of all the lords.
The duo consist of the Red King and the Yellow King. The Yellow King is a twelve-foot tall mute in yellow plate armor who wields an oversized falchion. He is the most physically powerful creature, though there are some who can outperform him using their magic, such as the chaotic evil lord. Though his falchion is his weapon of choice, he has taken the time to gain proficiency in dozens of exotic weapons as well. He has honed his skills to the point where he can find the weak spots in anything, and can critically hit all targets. This includes objects and even the very fabric of reality, and by cleaving holes in space-time he can create tunnels anywhere he wishes.
The Red King is half the size of the Yellow King, but is considered to be his equal in power. He is physically weaker and is skilled in fewer weapons, but his skill with his curved bastard sword is such that he can hold his own against the Yellow King when they duel. He is an expert in disarming opponents and finding holes in their defense. He is also possibly the most skilled smith in all the planes, due to his power to communicate with the spirits in all things and intimidate them into changing their physical and magical properties.
The two were briefly restored to life in the mortal realm by the party, and then stole power from an artifact of Mammon to bring their lordly powers back from the chaotic neutral plane. They shared this power with Charel/Cheryl/Chyrel, which caused her to become a Divine Guardian.
From the mortal realm, the Yellow King cut a hole into the true neutral plane, where they were forcefully kicked back to the chaotic neutral plane. They have been seen there again later, continuing their previous jobs, and presumably are no longer able to cut their way out.