Tawnos, Urza's Apprentice

An "artifact source" is a permanent, spell, or card in any zone with the card type "artifact." For example, Tawnos's ability can target a cycling ability you've activated if the discarded card is an artifact card.

If the activated ability's cost contains a choice, such as a creature to sacrifice or a number of counters to remove, the copy uses that same information. You can't pay the cost again, even if you want to.

In some cases involving linked abilities, an ability requires information about "the exiled card." When this happens, the ability gets multiple answers. If these answers are being used to determine the value of a variable, the sum is used. For example, if Soul Foundry's enters-the-battlefield ability is copied, two cards are exiled. The value of X in the activation cost of Soul Foundry's other ability is the sum of the two cards' mana values. As the ability resolves, you create a token copy of each card.