User blog comment:Long Patrol Girl/Essay: The Declining Mental Health of Antagonists of the Redwall Universe/@comment-1669318-20091127000358

That's because humans are much, much bigger than rattlesnakes, Asmodeus was probably bigger than Slagar, hence more poison injected and bigger fangs. If the venom can kill Ragear and Guosim, it could probably mess up Slagar's face.