Can I just get an extra **** hand? A claw? What about a set of pincers? Clamps? Something?
Seriously, they're all over the tech-priest artwork and lore but there doesn't seem to be much in the way of published rules found for the non-I-crush-your-hand-shaking-it-with-my-manipulator/servo arm-mechadendrite. Did I miss something? Anyone have any ideas on that or would it just need to be house-ruled as another form of manipulator mechadendrite without the STR bonus but can approximate standard arm/grip strength and manual dexterity (but not enough to step on the other mechadndrite's area of optimization)?
Otherwise....

