"But all the while the true enemy – the Black Ring – still festers beneath the surface, ready for its next move, poised to strike. For their leader Damian tirelessly plots silent schemes with utterly malign intent."
should be "ready for its' move".
Nope. The possessive "its" never has an apostrophe. It's written correctly the way it is.
BTW, how was "Dragons strength" ok in American english? You need the apostrophe there no matter which continent you're on.
