"[LV1][LV2] (Your Start Step) You can reveal 1 card from the top of your deck. If that card has ""FourShellSky"" in its name, you can summon it without paying the cost. If it is any other card or you choose not to summon it, return that card to the top of your deck. [LV2] While you have a Spirit with ""FourShellSky"" in its name on your Field, this Nexus cannot be destroyed and returned to the hand by opposing effects."