Warning : for sisters who prefer to find out TWSSG’s ending by watching the drama, please stop here. For sisters who like to continue to read my 'nonsense' analysis, please also stop here. Hahaha trust me, not that I know the details myself to warrant any intelligent analysis. I just can’t help but slip in my silly thoughts :)
To me, even though Damdeok is the chosen Jooshin King by heaven, unlike Lord Hwangwoon, he is still a human being. He feels guilt and remorse when he realizes he has accused Kiha wrongfully all along while she still loves him and even bears him a child. Our wise King has to make a royal decision on the spot after Kiha explodes into the black Joojak. After all, he cannot leave the fire-y Kiha dangling in the air for a few days while he takes his time to explain to his sacred guardians why he decides to destroy them. Or for that matter, to say a long lovey-dovey goodbye to his ‘2000 years’ love interest. So our dear Damdeok makes a quick noble and manly decision not to leave the mother of his child to die by herself, or should we simply assume that he gallantly walks into the affected site to try to extinguish the fire?? Maybe this later assumption is not that ridiculous since our Damdeok is always considerate and kind? Hehe, just kidding. I know this ending is probably more captivating than him and Sujini lived happily ever after in his palace, but still it’s heartbreaking to see our Yong Joon die one more time. It still bothers me to watch Cho Won and Jae Ho died, or even my beloved MinHyung going blind. Anyway, here’s my humble conclusion drawn from this last episode :
Damdeok is a fun buddy – he hangs out and laughs with his friends into the wee hours of the morning.

Damdeok is a protective boss – he fights for his employees’ territories and even their lives.

Damdeok is a faithful husband – he still loves the same woman even after 2000 years.

Damdeok will make a wonderful daddy – he teaches his son how to wash his hands before eating.

We will love and miss you, Damdeok! Yong Joon ssi, please rest well and have a speedy recovery :)