I have the game on iOS and just bought the Obsidian Edition on Steam. I've read through how to merge accounts and saw I've to choose a main account when merging. I would like to know would I lose anything from the non-main account? On my iOS account, I've bought many alts and dice but the Obsidian Edition gives me 1 of each card in the game. What happens when I merge these accounts?

They should merge nicely, but if it does not, I think that it is easier to use you mobile version as a Main account in this case because it is harder to say what gone missing if Something goes wrong.