What do you understand from this...?

Admittedly not much... but as for ysis, the 'yellow complexion' serves not only as literal descriptor but also connotes systemic illness or disease, even in the presence of abundance -- 'amid a sea of golden haze.' Thus even though the scarecrow is 'happy' or perhaps superficially contented, he cannot keep harm away; his jaundiced coloration suggests something is not quite right, something is rotten in Denmark! Then 'the antagonist in the book of motion,' which I presume is some formless entity that shapes destiny, 'gently smiles, quietly dances' as if to knowingly and silently gloat over his certain victory. He has the capacity to steal from the farmer that which the scarecrow cannot defend, viz. his life.By the way, in English 'quake' is an intransitive verb so you should not use a direct object like 'the farmer's house' with it. You would need 'shakes,' a transitive verb, instead. This was an oddly quiet and slyly malevolent little bit of verse, quite unsettling for this reader.