Do the effect in reverse. Follow any text to sand or disintegration tutorial and using the physics of Particular, spherical force field in Particular (set to a negative number), and some extra distortion effects (bezier warp maybe?) to make all the particles go to a specific point.
Time reverse the precomp.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
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