You were at the height of your power...
The Lands of Faerūn had learned of your name and recorded your deeds for all time. The adventures you undertook were epic, grand and most of all, highly rewarding to you. Yes, the Lands of Faerūn knew of you, and you knew them all too well in your many years of travels, the people you came across, kings bowed at your feet and gods took notice. Towns would throw parades in your honor, the Harpers invited you to join them, the Flaming Fist Mercenary Company wanted you to train them, and even Khelben Arunsun had asked for advice.
Again, you were at the height of your power on Toril. But, you are no longer on Toril. Crossing the actual planes of existence might have once been only a passing thought in your mind, but now it's the reality you must face.
Welcome to a place beyond the realms, a place you are not at all familiar with even with all of your experience. There are others here... and just like you they have been plucked from the various ages of the Realms at the height of their power.
Nature, nurture heaven and home,
...and together we'll cross the river