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While I could certainly seen Aurumoth being a standalone pokemon, I'm gonna have to go with everyone else and say Two pre-evos. Aurumoth strikes me as a pseudo-legendary, which all have two pre-evos, and pre-evos are just plain fun :)
Tempted to go with one, like Volcarona. However, the chance for bronze, silver, and gold evo line, plus the fact that the 600 BST indicates pseudo-legendary status makes me lean towards two.