Idrs had a long, flat, gray, segmented body with many limbs to help it move. It was also covered in small hair-like feelers and bristles to detect far off vibrations, allowing it to hone in on possible prey. These were so sensitive that it could detect individual targets out of a group and allowed it to plan its attack accordingly. For attacking purposes, an idr had razor-sharp mandibles as well as pincers.
The creatures were known to be particularly vicious, hunting to kill for pleasure rather than for survival. They were also very intelligent and could pull tricks even on witchers, feigning to go for one target but then going for the real one. Combined with its incredible agility, it made a formidable creature to come across.
- Geralt called it a type of arachnomorph, but in truth he didn't know what it was and feigned knowledge to not appear ignorant to the one who issued the contract.
- Other special breeds were draconid Vigilosaur and Parazeugl.