Real World MythologyEdit
The triskelion is an ancient symbol with wide and varied meanings and usage around the planet.
The triskele is widely considered a Celtic symbol, though it is pre-Celtic in origin and can, in fact, be found in numerous ancient cultures. The symbol has a variety of meanings: the stages of life and progress through life (action, moving forward, etc), reincarnation (connoted by the continuous, connected, spiral), the three realms (sky, earth, water), and, most appropriately, the phases of the moon (new, half, full).
Teen Wolf MythologyEdit
Derek's meaning for the symbol is how werewolves, an Alpha, Beta, or Omega can rise but fall to another status in a pack. A Beta can become an Alpha, but an Alpha can fall back down to an Omega.
Talia Hale used a cheap metal disk imprinted with a triskelion to help each of her children learn to control their shifts during the full moon.
Later, in Season 4, the tri-symbol is tied to the Buddhist mantra “Three things cannot be long hidden: the sun, the moon, and the truth" which is used by Satomi Ito's pack. It was eventually used in an effort to calm Liam Dunbar during an uncontrolled shift in Smoke & Mirrors.