I remember

I liked Kael from the Empyrean Odyssey series (even if I didn't really care for the ending) and his arc felt sort of cheapened when he never showed up... anywhere, after that.

But as with so much of 4th Edition (and in the great words of Adam Savage) my approach is "I reject your reality and substitute my own!" AND since we're working from a heavily altered timeline anyways, we can handwave any disparity in the timing of such introductions as "temporal lensing and distortion".