Mykdl'dy (Pronounced Mc-dil-ty) is a planet in the Monceros System.
Mydl'dy is tidally locked with its sun, so one side of Mykdl'dy always faces the sun, while the other does not.
The day side of Mykdl'dy is molten hot at 3,600°F (about 1,982°C) and the night side is -320°F (about -196°C). There is a narrow habitable zone in the middle of the two temperature extremes.
It appears that humans can't breathe Mykdl'dy's atmosphere, as Ben appeared to be struggling to breathe and passed out after he reverted to himself while on Mykdl'dy, Ultimate Echo Echo, Four Arms and Cannonbolt appeared just fine.
Necrofriggian colonists live on Mykdl'dy because neither the hot or cold climate affect them. They guard a quarter of the Map of Infinity in the temple. The temple has a series of traps, preventing people from getting the first quarter of the Map of Infinity, including Cerberus. The visitors must take a guide with them in order to visit the temple safely.
The planet's name is a pun on the McDonald's McDLT, famous for coming in two halves, one hot, one cold.