Sources : Griffin

Herodotus [c. 484 – c. 425 BCE] (Histories, Book 4.27) is from the Issedones that the tale comes of the one-eyed men and the griffins that guard gold; this is told by the Scythians, who have heard it from them; and we again have taken it for true from the Scythians... - [Godley translation]

Pliny the Elder [1st century CE] (Natural History, Book 10, 70.136): ...the griffin with ears and a terrible hooked beak I judge to be fabulous. - [Rackham translation]

Aelianus [170-230 CE] (On the Characteristics of Animals, Book 4, 27): I have heard that the Indian animal the Gryphon is a quadruped like a lion; that it has claws of enormous strength and that they resemble those of a lion. Men commonly report that it is winged and that the feathers along its back are black, and those on its front are red, while the actual wings are neither but are white. And Ctesias records that its neck is variegated with feathers of a dark blue; that it has a beak like an eagle's, and a head too, just as artists portray it in pictures and sculpture. Its eyes, he says, are like fire. ... And the people of Bactria, who are neighbors of the Indians, say that the Gryphons guard the gold in those parts; that they dig it up and build their nests with it, and that the Indians carry off any that falls from them. The Indians however deny that they guard the aforesaid gold, for the Gryphons have no need of it (and if that is what they say, then I at any rate think that they speak the truth), but that they themselves come to collect the gold, while the Gryphons fearing for their young ones fight with the invaders. - [Scholfield translation]

Gaius Julius Solinus [3rd century CE] (De mirabilibus mundi / Polyhistor, Chapter 15.22): While these lands [Asiastic Scythia] abound in gold and gems, the gryphons hold universal sway over them. Gryphons are extremely ferocious birds, and have a rage worse than any madness. Owing to the necessity of facing the gryphons’ cruelty, the approach of visitors is rare. Indeed, the gryphons mangle anyone they see, as though born to punish the rashness of greed. - [Arwen Apps translation, 2011]

Isidore of Seville [7th century CE] (Etymologies, Book 12, 2:17): The griffin [grypes] is so called because it is an animal with feathers [perhaps grus, “crane”] and four feet [pes]. This kind of wild animal is born in the Hyperborean mountains. They are lions in their entire torso, but they are like eagles in their wings and faces. They are violently hostile to horses. They also tear humans apart when they see them. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Birds 5.52): Griffins are birds, as Jacobus and Pliny say, that are exceedingly violent in their large bodies, so much so that they overcome and kill armed men by preying upon them. But their hooves are of such great capacity, that skiffs are made of them suitable for human use. In Asiatic Scythia griffins keep gold and gems in a certain inaccessible place, and because they attack foreigners, access there is rare, since they pluck men as if they had been sent by God to punish the rashness of greed. The Arismaspis fight with these in order to seize the emerald stones, the kind of which is the most valuable in their region. As it is found in the gloss of the book of Exodus, where these birds are said to be prohibited by law, this bird is four-legged, with a head and wings like an eagle, although much larger; with the rest of his body it imitates a lion. And it dwells in the Yperborean mountains, and is most fierce to horses and to men. As the Experimentator says, the griffin puts an agate stone in its nest, no doubt but for some remedy. It is clear, therefore, that the stones were given by God for some remedy. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book12.19; 18.55): [Book 12.19] A Gripe is called Griphes, and is accounted among Volatiles Deutronomi. 14. And there the Glose sayth, That the Gripe is foure footed, and lyke to the Eagle in head and in wings. And is like to the Lion in the other part of the body, and dwelleth in those hilles that be called Hiperborei, and bée most enimies to horses and men, & gréeveth them most, & layeth in his neast a stone that is called Smaragdus, against venimous beasts of the mountaine. [*Book 18.55] Grifes the Gripe, is a beast with wings, & is foure footed, and bréedeth in the mountaines Yperboreis, & is lyke to the Lyon in all the parts of the body, & to the Eagle onely in the head & wings, and is strong enimy to the horse: as Hugution saith, he taketh up the horse and the man armed, as the Glose saith super Deut. 14. And Gripes kéepe the mountaines, in the which he Gemmis & precious stones, as Smaragdus and Jaspis, and suffer them not to be taken from thence, as Isi[dore] saith, li. 14. ca. 3. And in some countries in Scithia is plenty of gold and of precious stones: but for great gripes men dare not come thether openly, but seld for fiercenesse of Gripes: There is best Smaragdus & Christall: & the Gripe hath so great clawes & so large, that of them bée made cups that bée set uppon boordes of kings. - [Batman]

Cecco d'Ascoli L'Acerba [early 14th century] The griffin fears poisonous animals and keeps an emerald in its nest for protection.