As you've noticed, your solution can't involve striking the orb, because that would shut off the stairs. So don't strike the orb! There's another way to get to the serpent area.
The level's introduction implicitly states that whatever is written on the scroll will be helpful. The scroll says that briars can destroy just about anything. This is useful because...
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×Briars can destroy
orbs. Now, if briar grows into the space where the orb is, the orb will be destroyed. A new problem arises, though... briar is now blocking that space.
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×If you light the fuse with proper timing, the briar will destroy the orb but get blown up with the bomb very quickly. You can then race past it into the passageway before it grows again.
Hopefully that should help you out. There's still plenty left to this hold, so don't give up!
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Quick links to my stuff (in case you forgot where it was):
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