Monta tervedis, Laura Elizabeth, Ei talen elleama vel selen silen loestel!
Oh my, that brought a scary image...
Some of them have turned to the enemy, so as far as riders, goblins and sorcerers would probably ride these. Some also have joined the side of light, and perhaps the dwarves would be able to ride them, but dwarves prefer the feel of stone beneath their feet...
As far as colors, I normally picture them like giant grey wolves, but some could be brown and some black as well.
Their claws are the same size in comparison to their body size as a regular wolf's claws are to their size. Their teeth are the same way, with the exception of the canine teeth, which are replaced by hollow fangs like those of a serpent, which are linked to a sac containing potent venom.
I hadn't thought about how they would live, but probably in mating pairs for life, with bachelor males traveling in small bands together until locating a mate.
I've not decided whether or not they can talk. I was thinking of having a complex language of growls and barks, used in conjunction with different body languages to communicate, but they are certainly capable of rational thought.
In history past there have been times when Elvurs have befriended elves and fought alongside their previously mortal enemies, but that has been rare.
That I have not thought of either, probably around two or three pups per litter.
The best way to kill one would be to shoot just behind the front shoulder in hopes of getting the arrow to hit the heart and lungs, but due to their size it is extremely difficult, one would need to be an expert archer with an extremely powerful bow. The other option would be to enter Illnorean (if one is an elf) and dodge to the side as the Elvurs charges while cutting for the neck. Another option (if you're a dwarf) would be to plant your pike as it charges and hope to get it in the throat as it charges. All of these options are extremely difficult, and very rarely successful.
Thank you for all the questions!