[Felisin Fatter]

A new theory: During FoD, the dragon blood is already spreading. Like this:

1 - Draconus somehow mates with Tiam (or another dragon). The result of this is Arathan. Draconus and Arathan both have dragon blood, this is the reason Arathan was kept 'chained' and hidden and that he has to be far away now, when chaos approaches. This must have been fairly recent, as Arathan is a few years-decades old (he claims to be 17 but his memories are very fuzzy). It could be a bit longer if Draconus has kept Arathan 'frozen' and chained for a longer time.
2 - Draconus makes a deal with Olar Ethil (or she seduces him), leading to the triplet and to the spreading of his dragon blood to Olar Ethil. This is how she becomes Dragon soletaken and when she learns how to give her bonecasters shapeshifting too. Or she only becomes Olar Ethil by doing the ritual. This ritual binds her strongly to the Imass though, making her less in control of her own apperance and personality. When we meet her, she is still adjusting to this.
3 - Shapeshifting is also given by someone to the Jheck and Jheleck.

Alternatively, Draconus might just be a dragon. The name could be a hint...