The infamous Shyvana’s copypasta first appeared from an anonymous comment under her NSFW art early 2013. It was later expanded and used as a comment in a popular League AMA which brought it into mainstream popularity.

Vaginas exude a large amount of heat on normal human women, let alone on certain female half-dragons, whose body temperatures would only naturally be much higher than a normal human's. If one were to approach Shyvana's bare vagina, especially if she was aroused, you would probably be able to feel the heat of it on your skin. The natural heat is also probably conducive to arousal in its own right. Much like a 15 year old going through puberty and getting erections at random, a side effect of being a half-breed is probably often, unprovoked arousal. Who knows, it may even be permanent. Shyvana might literally be "in heat" at all times. On top of what may be almost perpetual wetness between her thighs, her naturally high body temperature probably makes it difficult for her to wear human clothes comfortably (especially tight, reinforced armor). She probably sweats profusely in her armor, enough to drench herself in only one short outing to Summoner's Rift. But then again she may get off on the feeling of being wrapped so tightly, so to speak. The sensation of her wet vagina would probably resemble putting your finger into a bath of hot honey. The juices more viscous than normal and just hot enough that you almost risk a burn. Imagine the smell and the taste of her inner thighs after one match. Wet and sticky with a musky odor and all salty-sweet from the combination of her various juices...

In addition, Shyvana's vagina may even be larger than those of human women, or at the very least anatomically different. The vaginal walls of human women only contract significantly during sex if experiencing orgasm. Due to her half-dragon nature, Shyvana may resemble some member of the known animal kingdom in that her physical control over her vaginas muscles is much greater. It would not be unreasonable to suggest that Shyvana could flex and contract the muscles in her vaginal walls to masturbate and in effect "milk" a penis for all it's worth. Her cervix may even be penetrable with little to no pain experienced, a sort of inverse "knot", a way to ensure that not one drop of her mate's semen will escape her.

The thing about Shyvanna is...

Vaginas exude a large amount of heat on normal human women, let alone on certain female half-dragons, whose body temperatures would only naturally be much higher than a normal human's. If one were to approach Shyvana's bare vagina, especially if she was aroused, you would probably be able to feel the heat of it on your skin. The natural heat is also probably conducive to arousal in its own right.

Much like a 15 year old going through puberty and getting erections at random, a side effect of being a half-breed is probably often, unprovoked arousal. Who knows, it may even be permanent. Shyvana might literally be "in heat" at all times. On top of what may be almost perpetual wetness between her thighs, her naturally high body temperature probably makes it difficult for her to wear human clothes comfortably (especially tight, reinforced armor).

She probably sweats profusely in her armor, enough to drench herself in only one short outing to Summoner's Rift. But then again she may get off on the feeling of being wrapped so tightly, so to speak. The sensation of her wet vagina would probably resemble putting your finger into a bath of hot honey. The juices more viscous than normal and just hot enough that you almost risk a burn. Imagine the smell and the taste of her inner thighs after one match. Wet and sticky with a musky odor and all salty-sweet from the combination of her various juices. 

Original

"Vaginas exude a large amount of heat on normal human women, let alone on certain female half-dragons, whose body temperatures would only naturally be much higher than a normal human's. If one were to approach Shyvana's bare vagina, especially if she was aroused, you would probably be able to feel the heat of it on your skin. The natural heat is also probably conducive to arousal in its own right. Much like a 15 year old going through puberty and getting erections at random, a side effect of being a half-breed is probably often, unprovoked arousal. Who knows, it may even be permanent. Shyvana might literally be "in heat" at all times. On top of what may be almost perpetual wetness between her thighs, her naturally high body temperature probably makes it difficult for her to wear human clothes comfortably (especially tight, reinforced armor). She probably sweats profusely in her armor, enough to drench herself in only one short outing to Summoner's Rift.But then again she may get off on the feeling of being wrapped so tightly, so to speak. The sensation of her wet vagina would probably resemble putting your finger into a bath of hot honey. The juices more viscous than normal and just hot enough that you almost risk a burn. Imagine the smell and the taste of her inner thighs after one match. Wet and sticky with a musky odor and all salty-sweet from the combination of her various juices..."