Complex sentence: During the battle with the X-Men after Longshot had found the missing artifact they were searching for, Rattler created an avalanche by rattling his tail, though this took both Longshot and Rattler out in the process.
Split into simpler sentences: During the battle with the X-Men after Longshot had found the missing artifact they were searching for, Rattler created an avalanche by rattling his tail. Unfortunately, it took both Longshot and Rattler out in the process.