When Matter Reshaper dies, reveal the top card of your library. You may put that card onto the battlefield if it's a permanent card with converted mana cost 3 or less. Otherwise, put that card into your hand.
If you put an Aura card onto the battlefield this way, you choose what it enchants as it enters the battlefield. You must be able to choose a legal player or permanent or you can't put the Aura onto the battlefield.
If you don't put the card onto the battlefield for any reason, you put the card into your hand.