Counter target spell. Create X colorless Treasure artifact tokens, where X is that spell's converted mana cost. They have ", Sacrifice this artifact: Add one mana of any color."
9/29/2017 For spells with in their mana costs, use the value chosen for X to determine the spell’s converted mana cost.
9/29/2017 You may target a spell that can’t be countered. When Spell Swindle resolves, the target spell will be unaffected, but you’ll still get Treasures.