Treasure Keeper
Artifact Creature — Construct
When Treasure Keeper dies, reveal cards from the top of your library until you reveal a nonland card with mana value 3 or less. You may cast that card without paying its mana cost. Put all revealed cards not cast this way on the bottom of your library in a random order.
Illustrated by
Foundations Jumpstart#760UncommonEnglishLegality
Rulings
If you don’t cast the nonland card with converted mana cost 3 or less, it’ll be put on the bottom of your library in a random order with the other cards.
If you cast a card “without paying its mana cost,” you can’t choose to cast it for any alternative costs, such as paying 
to cast a morph card face down. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Cathartic Reunion, those must be paid to cast the card.
If the card has 
in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
If your library has no nonland cards in it with converted mana cost 3 or less, you’ll reveal all the cards in your library, then put them in a random order. Although this is not technically shuffling your library, no player is allowed to know the order of those cards and you will randomize the cards in your deck.