Cascade triggers when you cast the spell, meaning that it resolves before that spell. If you end up casting the exiled card, it will go on the stack above the spell with Cascade.

When the Cascade ability resolves, you must exile cards. The only optional part of the ability is whether or not your cast the last card exiled.

If a spell with Cascade is countered, the Cascade ability will still resolve normally.

You exile the cards face-up. All players will be able to see them.

If you exile a split card with Cascade, check if at least one half of that split card has a converted mana cost that’s less than the converted mana cost of the spell with cascade. If so, you can cast either half of that split card.

If you cast the last exiled card, you’re casting it as a spell. It can be countered. If that card has cascade, the new spell’s cascade ability will trigger, and you’ll repeat the process for the new spell.

After you’re done exiling cards and casting the last one if you chose to do so, the remaining exiled cards are randomly placed on the bottom of your library. Neither you nor any other player is allowed to know the order of those cards.

Maelstrom Nexus affects the first spell you cast each turn, not just the first spell you cast on your own turn.

If the first spell you cast in a turn already has cascade, both cascade abilities will trigger separately. Deal with them one at a time: First one cascade ability will resolve, and you’ll cast the applicable card if you want. That new spell will resolve. Then the other cascade ability will resolve in the same way. Finally, the original spell will resolve.

This effect takes into account spells that were cast earlier in the turn that Maelstrom Nexus entered the battlefield, including any spells still on the stack. If you’ve already cast any spells that turn (including Maelstrom Nexus itself), this ability won’t give any of your spells cascade that turn.

A spell’s converted mana cost is determined solely by the mana symbols printed in its upper right corner. If its mana cost includes , take the chosen value of X into account. Ignore any alternative costs, additional costs, cost increases, or cost reductions.