Help with Narnia

In the translation of The Lion the Witch and the Wardrobe, I came across this sentence. Edmund has just happened upon a motionless lion:

No se había movido ni una pulgada desde que lo descubrió.

The use of se in its many forms is often a point of confusion for me. In this case is it part of haberse (which SpanishDict says means "to have it out" and doesn't work here), or is it somehow reflexive? Is it connected to mover?

submitted by /u/aldenoneil
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