Siletta is the last obstacle to the Dragon Temple treasury of Wyrmroost. She is known as the "The Poisonous One" due to the fact that she is poisonous to the core. Quote, "Her breath, her flesh, her blood, her tears, her excretions, everything is deadly poison.You saw how I looked? That was simply from being in the same room with her. Everyone should touch the horn. Even out here we may be getting exposed." (Fablehaven: Secrets of the Dragon Sanctuary, Gavin) She resembles a giant salamander with at least 10 sets of legs, that is very long and agile. She has translucent skin, that revealing veins and colorful organs. She is so poisonous that just being inside her toxic lair will kill you, lest she breathes on you. She used a black, slushy, poisonous substance to destroy Mendigo, but through the power of the first horn of the unicorn, Seth and Kendra were saved. Seth and Kendra also used the horn (constantly recharged by Kendra's energy) to quickly kill Siletta.
To learn more about the Poison Dragon's variation, the Dark Poison Dragon, read the Dark Poison Dragonpage.