I somehow had an hypothesis come to mind about one of Strength's possible origins. Take that with a grain of salt but:
When Dragon used to be religious, did he used to pray? Praying is a very similar exercise to narrating / forcing, so maybe praying would have created a thoughtform he was talking to. And when he stopped being religious, he stopped "praying", and thus stopped narrating / talking to Strength. And thus, Strength felt abandoned when Dragon "abandoned" his religion.