#comprasion

Both places having a similar skyline and a big, blue power crystal (Heart of Atlantis and Power of Laputa)

Both housing magitek robots, which defend the cities during an assault (the Stone Guardians and Laputas robots)

Both locations having a writing system unknown to the surface people (Atlantean and the Laputa glyphs)

In both cases, only Royals are able to channel the Heart Crystals power

Both Thalia and Callum are peaceful magic users, who can also get dangerous when needed

Daiman and Rayla are skilled warriors, but lacking the will to kill. But not a ruthless side when it calls

Both couples having some arguments because of their different cultural viewpoints. Thalia and Callum didnt understand some elf customs, while in turn Daiman and Rayla having still alot to learn about fairy/human culture.

One half is (part) Asian (Callum/Daiman); the other white (Rayla/Thalia)

Both have to deal with an treacherous advisor (Pheadon/Viren)

Both hold a grudge for 1000 years after the loss of a loved one (Aaravos after Leola's death; Demona after the destruction of her clan)

Both are immortals; but it works different for each (Demona had her connection to Mcbeth; Aaravos is simply from a immortal species of elf)

Both wanting revenge on the ones who wronged them, until doomsday when needed (Aaravos on the Cosmic council; Demona on humankind)

Aaravos started to move on, while Demona is blind for the option of a fresh start.

Both can turn into humans. (Demona only at day)

Both species are very arrogant and suffering of god complex. The star elves are obsessed with order; the sun elves wanting to be the elf leaders of Xadia.

And they have - with well-known exceptions - little to no emotional connection to other beings like humans or other elf races.