Complex sentence: For the first time ever, the doors to the shop are closed as Yvars arrives which is perceived as Lasselle; the boss wielding his power over his employees one last time after successfully dismissing their demands.
Split into simpler sentences: For the first time ever, the doors to the shop are closed as Yvars arrives. This is perceived as Lasselle (the boss) wielding his power over his employees one last time after successfully dismissing their demands.