NO DRAGONS!?

I don't think that traditional Western Fantasy-style dragons make much sense in the setting of Path of Exile. There are no elves and dwarves to go along with that. I'm not too familiar with Maori or Aboriginal mythology, but seeing some of the dragon-like creatures from their mythology make an appearance might be interesting. The Maraketh have an Asian flair to them, as well - seeing Chinese-style dragons could be worthwhile.

The other option, of course, is to see more gribbly and cosmic-horror style 'dragons' as from works in the style of H.P. Lovecraft; see the dragons in Privateer Press's Iron Kingdoms setting who are basically sentient radioactive life forms with some strange stranglehold on divinity, or the genetically engineered murder machines from R. Scott Bakker's Second Apolcalypse series.