Since the gold Power potion could be used multiple times, it was what separated the spirit guardian knight captain from the rest of the spirit guardian knights. The current spirit guardian knight captain was basically totally immune to ice and fire attacks. But of course, it was under his defense limit.
As far as Abel knew, Rakanishu had 2 main abilities. The first one was speed, which Abel had just experienced its power through Rakanishu's attack. The moment when Abel's first arrow struck Rakanishu, it had already rushed in front of him. This special ability to charge allowed the 2 little legs of Rakanishu to accelerate even faster than Black Wind in a short distance.