Both the Talisman of Pure Good and the Talisman of Ultimate Evil deal damage to creatures of the wrong alignment who touch them (6d6 to neutrals and 8d6 to the exact opposite alignment). Here is the relevant passage for the Talisman of Pure Good:
A creature that is neither good nor evil in alignment takes 6d6 radiant damage upon touching the talisman. An evil creature takes 8d6 radiant damage upon touching the talisman.
What I'm wondering here is whether the contrary is true: if a creature of the wrong alignment gets touched by such a Talisman, would it take damage? And if so, what would be the mechanics of trying to attack a wrong-alignment creature with a Talisman if you are of the right alignment yourself?
- None, the target has to willingly touch the Talisman to be damaged by it and/or touching =/= being touched by.
- Unarmed strike on the target with the Talisman, dealing the damage on a hit (works with Extra Attack).
- Same, but Improvised Weapon instead of Unarmed Strike.
- Action to try to touch the target with the Talisman, who may get a Dexterity saving throw (against what DC?) to avoid it.
- Grapple check (Athletics VS either Athletics or Acrobatics), dealing the damage on a success (either in addition, or instead of, the grappled condition).
- Other mechanics.
Another thing to wonder is, if option 2 or 3 is the right one, whether, in addition to the 6/8d6 damage, the normal unarmed strike / improvised weapon damage would also apply.
I personally believe it would be option 3 (plus the regular improvised weapon damage), but it's better to verify on this site.