Complex sentence: After following Ronin into the portal, the ninja have a final battle with Ronin who escapes but in the process knocks the ninjas weapons out of their hands and into the endless abyss.
Split into simpler sentences: After following Ronin into the portal, the Ninja have a final battle with Ronin. He escapes, but in the process, he knocks the Ninja's weapons out of their hands and into the endless abyss.