This is a general idea -- I'd like seven dragons intertwined together, sort of like a circular mandala. These dragons are in a special arrangement that is my world's equivalent of the Ark of the Covenant, the depiction of the ultimate deities who created the world, will destroy it, and will perfect it
The Hydra, an ancient serpent-like chthonic water beast that possessed many heads , the poets mention more heads than the vase-painters could paint, and for each head cut off it grew two more, it's poisonous breath and blood were so potent, even its tracks were deadly. The Hydra of Lerna was killed by Hercules as the second of his Twelve Tasks
Lernaean Hydra - water monster with reptilian traits and multiple heads - Greek Mythology; Although I know that in most of the stories the Hydra has nine or twelve heads, there are different approaches on the number of heads: it was believed to have only one head in the beginning and as soon as someone tried to chop that head of, two new heads grew.
Balaur (Romanian) - A feral hydra breed that is probably the result of a hydra mating with a dragon. They are much more powerful than normal hydra's. When you cut off a head of this creature two more powerful heads grow back instead, but they are extremely fragile to fire attacks.