If the chain item does not fulfill the conditions by the time step 5: check legality has been reached, the actions taken while playing it are undone and it is returned to the zone it was played from if it is a card.
§ 806.4.b Core Rules PDF (officieel)
§ 806 Action
§ 806.4 Some passive abilities may grant a card or ability Action under certain conditions. The card or ability does not have the Action keyword unless and until those circumstances are true.
