Thorough Investigation (AFC) from Forgotten Realms Commander, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Aaron J. Riley
• Card Text:
  Whenever you attack, investigate. (Create a colorless Clue artifact token with "2, Sacrifice this artifact: Draw a card.")
  Whenever you sacrifice a Clue, venture into the dungeon. (Enter the first room or advance to the next room.)