As with all of the Vile Four, their reincarnations, and the Dark King, Twinhead Wyvern has four phases to the battle, depending on how much HP it has left. The first phase has its right head facing the player and the left head facing to the side. After losing a quarter of its health, the right head is reduced to a stump. After losing half of its health, the remaining head takes over the body. After losing three-quarters of its health, the creature's head is lowered and the wings are left tattered.
wyvern is a medieval European mythological winged creature with a dragon's head, reptilian body, two legs (sometimes none), and a barbed tail. They appear in many crests of Europe's ancient families, symbolizing strength. The word wyvern comes from wivere, which means serpent.A
In Germany, the boss is called "Siamdrache" meaning "Siamese Dragon". This is not in reference to hailing from Siam, but rather by being conjoined (or Siamese) twins.