Culling Scales

• WWizards of the Coast2004-12-01
  Official Ruling
  Most tokens have a mana value of 0. A token that's a copy of another permanent or card has a mana value equal to that permanent or card's mana value.
• WWizards of the Coast2004-12-01
  Official Ruling
  If the targeted permanent doesn't have the lowest mana value when the ability resolves, the ability doesn't resolve and the permanent isn't destroyed.
• WWizards of the Coast2004-12-01
  Official Ruling
  If the lowest mana value is 3, Culling Scales can destroy itself.
• WWizards of the Coast2004-12-01
  Official Ruling
  You choose the target. If there's more than one nonland permanent tied for lowest mana value, you choose which one to target.

Rulings via Scryfall