From Archon Arcana - The KeyForge Wiki

If two game elements are swapped, they exchange places with one another. If there are not two eligible game elements, the swap does not occur.

When two creatures in the same battleline are swapped, they exchange positions. This means that each takes the position in the battleline of the other. The two creatures swapped must always be controlled by the same player.

If cards from two distinct game areas are swapped (such as a card in play and a card in hand), the cards switch game areas, maintaining the order of the cards in the game areas as required.

KeyForge Master Rulebook v17.3 March 2024