If you are looking for quality models like dragons, golems, spiders, demons, devils, serpents, and much more, you are in the right place. Infinity PBR series contains not only beautiful models, animations, but most of them also have suitable sounds, music or even concept arts. The biggest advantage is that you have substances which you can customize to achieve a completely different result. On top of that, most packages have blend shapes to change the shape of well-known models. 

But words won't reflect the quality, so check Infinity PBR profile on the Asset Store.

You can also check their website, where you can subscribe and get a massive discount to fill your mobs, and enemies library quickly and painless for your wallet.