TheWanderingMist
Paladin of the Snow Queen
And then leave it to Sabrina to train while going to another region ...
In OS Why did Haunter follow Ash?
It was interested in him after hanging out with him for a while. And then Sabrina clearly needed it more as it would be able to keep her from getting too intense about her powers so I'm assuming that's why he left Haunter with her the first time.