Crystal Skull, Isu Spyglass

Some abilities trigger “whenever you cast a historic spell.” Such an ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.

You must pay all costs and follow all timing rules for spells cast from the top of your library this way.

If the top card of your library changes while you’re casting a spell, playing a land, or activating an ability, you can’t look at the new top card until you finish doing so. This means that if you cast a spell from the top of your library, you can’t look at the next one until you’re done paying for that spell.