घोररूपाः dreadful appearance, निशाचराः night rangers, महाभीमैः very fierce तैःवानरैः those Vanaras, वीर्यात् violently, वृक्षैः trees, अभिहताः beaten up, रणक्षितौ fell on battlefield, व्यचेष्टन्त hit one another

Night rangers of dreadful appearance beaten up with trees by most fierce Vanaras, fell on the battlefield and struck one another.