Strengths: very high jump, very fast and agile, long and powerful arms, spikes on head.
Weaknesses: limbs easily severed, effective attacks often involve difficult jumping procedures, natural weapons are not as effective as a sword for things like blocking (they have a tendency to get cut in two...as far as I know that doesn't happen to the sword)
These insectoids are dangerous indeed. Their long sweeping arms frequently chop my feet off (much to my annoyance!!), and they can jump considerable distances. Approach with caution, and patience...they can be worn down as long as you can dodge pretty fast. My personal favorite way of dealing with them is leading them into a room full of orcs or ogres (which by the way the mantis usually either kills or severely wounds in the process). One on one with a normal orc grunt I'd put my money on the mantis. I've even lured a mantis into the altar room with the orc shaman (just as a decoy) to find that it killed the orc lieutenant and shaman!! Their fighting is variable...be careful.