Hand Change is a term that refers to putting the same number of cards from your hand into your deck or graveyard, then putting the same amount into your hand.
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There are various ways this type of effect has been used.
Shield trigger (When this spell is put into your hand from your shield zone, you may cast it immediately for no cost.) ■ Each player counts the cards in his hand, shuffles those cards into his deck, then draws that many cards.
■ Evolution—Put on one of your Grand Devil. ■ Fort Energy—Deep Marine (When you put this creature into the battle zone, if a Deep Marine in your mana zone is tapped to summon this creature, this creature gets the following ability.)
Choose a creature in the battle zone and return it to owner's hand.
■ Fort Energy—Grand Devil
Choose a player. That player shuffles his hand into their deck, then draws the same number of cards.
When the card is considered to be discarded, you may only draw the same number of cards that are put into your graveyard. If you put a Madness creature into the battle zone instead of your graveyard, do not count that card in the number of cards that you draw.
There are 2 forms of Hand Change where the card can be discarded, or shuffled back into the deck. By returning cards to the deck, you can draw new cards without worry of being milled and having no cards left in your deck, but self-discard cards also have the option of Graveyard Fertilizer for reanimate combos.
This was mainly introduced and featured on a higher amount of Fire cards after the Episode 3 block.
In Duel Masters, water's hand exchange effects often follow a "draw, then discard" pattern, while fire's typically use a "discard, then draw" pattern.
From the perspective of improving hand quality, the former is generally more convenient. However, the latter often draws a fixed number of cards regardless of how many were actually discarded, allowing it to function as hand replenishment when your hand is low.
In Magic: The Gathering, the ability to exchange cards in hand is often referred to as a "looting" ability, named after the card Merfolk Looter.