Complex sentence: He is put on trial, however it turns out to be a mere kangaroo court where the judge immediately finds Mario guilty and orders him to clean up the graffiti and recover the Shine Sprites; he is forbidden from leaving the island until he does so.
Split into simpler sentences: He is put on trial, however it turns out to be a mere kangaroo court where the judge immediately finds Mario guilty and orders him to clean up the graffiti and recover the Shine Sprites. Until then, he is forbidden from leaving the island until he does so.