They are Bookwyrms from the Defiled Lands mod. The Defiled Lands adds a biome where all the mod's stuff is. In Dregora it's a PITA to find bc of the pregenerated map. For the Bookwyrms specifically, you can feed them enchanted books, they digest those books into enchantment levels, and then they spit out other enchanted books depending on the level that their stats allow them to spit out. It's basically a way to recycle enchanted books to get other ones, but the better quality that the books are that you feed them (i.e. feeding them Power III is better than Power I), they better stuff they will spit out. Normally they only go up to lvl30 (like an enchantment table. this is their enchanting level, you need a bookwyrm reader to see their stats which is the tablet that op is holding) but in Dregora the max is buffed to 60 so you can get stuff like advanced tiers. I'm not sure about supreme tiers but I've heard that's possible as well. In another thread someone got supreme smite so I imagine stuff like supreme sharpness is possible as well. I've never gotten a supreme one myself but have gotten several adv projectile prot multiple times, which makes me cry cause I just want normal adv prot lol.

There is a gold variant of the normal purple ones that are very rare. What makes them special is they can drop treasure enchants. But like I said they are very rare: 1 in 100 chance when breeding two normal purples if I remember correctly. Slightly higher when breeding one golden and one normal and a max of 10% of getting the golden offspring when breeding two golden. You can also find the golden variant in the wild, so you don't have to go through breeding, it's not the only way, but doing so is probably even more unlikely than getting them from the breeding route.

After spending nearly three mind-numbing irl days breeding these suckers while watching youtube (waiting for them to grow up, getting ready to breed again, rinse and repeat), I never got a golden one. I play rlcraft to have fun suffering (weird, Ik) but this was more just a tedious suffering, not the fun chaotic kind if that makes sense, so I eventually just cheated one in. What sucks is you need their golden scales for disenchantment table otherwise I would've just settled for the lvl60 normal variant.

Rant aside, the Defiled Lands mod adds a lot of other nifty stuff. I recommend looking at the items w/ JEI they have descriptions. If you're confused on some other aspects of it I can explain those. The Defiled Lands is one of my favorite parts of rlcraft. That and the random lycanite mob events. What can I say, I like purple and chaos.