The Avernic Defender is the best defender in game, as well as being the second best melee offhand in game. It requires 70 Attack and Defence to wield. It has some incredible defensive bonuses, some solid melee accuracy bonuses, and a respectable +200 melee strength bonus.
Although it is quite powerful, the Avernic Defender does not see a lot of use. It is significantly rarer than the best-in-slot melee offhand, the Inferno Spirit Shield, and is therefore hard to find and not much cheaper.