This strat is called Ouroboros and it is miserably difficult. It's probably the hardest strat I've done in any speedgame in my life. This is my second (and fastest) success after an estimated 5000 or so attempts.
It is hard because:
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Henry (the rat) must be dropped in such a way that he walks to the left on a specific pixel, while the player dashes to the right.
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Getting Toragos (the bone snake) to turn up rather than down requires that the player be higher than him on the frame that he makes the decision. Doing this requires a "super boost jump" which is a frame perfect input.
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If both of those things are successful, the player must then to a perfect ice block jump, which is an extremely difficult (single pixel / frame?) jump off of the falling ice block.