Lightning, water, and fire! Like forever before the plot starts. By the time the plot starts, the lightning and fire deities have been subjected to punishment by the two gods that picked them.

Oh (the fire deity) is first to be punished. They basically decide that since they're going to live for a long time, gotta set some long time goals! And they opt to be the wrath of the gods since most of the other deities are too 'soft' in their opinion. So Oh just. Smites humans. This isn't really a /good/ thing and in their defense mentally, they do it to help Ymber since he's the softest of them all. So their punishment by the gods is to be split in two, effectively halving the power of one into two. (Now they are in a male and a female body and use both male and female pronouns apart since they together make they but apart it feels weird to be they. But prior to the split they use they/them. Also the split bodies go by the names Ohiwe and Ohime.)

Fulj is the second to be punished. She falls in love with a mortal woman and that is a crime according to the gods. Mortals and immortals are not to be together and it will only bring suffering to both sides. So her punishment is her memories of the woman are stripped and her body basically broken to the point she can't remain physical all the time.

Ymber, unfortunately, is the one who blames himself for the discoveries and punishments. If he had only tried to restrain Oh more then maybe they would have chilled out and stopped before being punished. If he had only tried to persuade Fulj to not continue seeing the mortal woman so often perhaps she wouldn't have been punished. So he's just increasing the guilt on his shoulders every day that he remains unpunished since the elder gods have both laid down to rest. They can't enforce their laws anymore and none of the deities are keen on harming one another at this point. They just want to continue existing in peace.