Talismans are very special items: they're the source of your hero's power. All heroes start the game with one talisman and must always have one (and only one) on them at all times. There are others that can be found or earned and your hero will have the option to pick which they want to use. Besides letting your character be a super hero, each talisman always has at least one benefit and one weakness.
Powerful talismans may have several of each. Which you choose is up to you, and you can switch them at any time, but the switch comes with a terrible price: part of your experience is locked up inside the talisman you wear, and switching to another drains your hero of 10% of his or her experience points (capped at 20,000 XP). The hero does not lose any skills or levels, but must regain the XP before being able to advance any further.
There is also a Talisman Transmogrifier in the Hideout, which allows your hero to drastically alter their starting talisman, an act so drastic it changes the hero's class and resets your hero all the way to level 1.