However, the Spirit still needs to pay any costs associated with using the Power, whether that's a mandatory "Cost to Use" (e.g., for Absolute Stasis) or a cost associated with a particular choice (e.g., for Hazards Spread Across the Island). You can pick a Power Card with a Cost to Use that you can't afford; in that case, you fail to use the Power and then Forget the card. Tags: Cost To Use, Resolving Powers, Ethereal Conjunction, Absolute Stasis (Fractured Days Split the Sky), 3 more...
While this tends to be pretty obvious when the cost is paying Energy, it's less clear if the cost is performing some other effect, like discarding a card or removing Presence.
There are no adjacent lands to add Blight to, so Blight does not cascade.
Push can't Push anything (unless you can Push to a land 2 away - eg, Many Minds Move as One - and there's a land 2 away, see below).
Whether you can target the land depends on whether you can measure Range from your Presence to it. If you made a disjoint land via Cast Down into the Briny Deep + Absolute Stasis, yes, because the land is Range 2 from other lands. But if you completely wall off a land via Repeats of Absolute Stasis, then there's no way to measure Range to it, so the only way to target Powers there would be to either have Presence in the land or the ability to ignore range (eg, Finder of Paths Unseen).
Note that Isolate is NOT usually sufficient to generate any of these situations, since it only affects adjacency for Invader pieces (JE rules, p. 10). Tags: Island Boards, Push, Range, Targeting, 2 more...
What happens if Cast Down into the Briny Deep sinks a board where a land is under Absolute Stasis? If you wantand you have a convenient coaster or other object that can represent the Stasis'd land, then the Stasis'd land survives. If it is disjoint from the rest of the island, consider it Range 2 from the land(s) nearest to it, per the Archipelago rules in Jagged Earth. If you don't want to do this, or have no convenient way of representing a single land, then Cast Down into the Briny Deep overwhelms the Stasis, ending its effects and affecting the land normally.
If by doing this you create a land with no adjacent lands, see this FAQ for how, e.g., Blight Cascades work.