We can usually expect split cards to be pretty tame, to keep them from becoming overpowered in Standard. But Expansion // Explosion has been flying under many players’ radars ever since the set was first spoiled.
On the surface, this looks like a more expensive and less powerful Sphinx’s Revelation. Once you have a bunch of mana available, you usually want things to help prolong the game, and that’s where the life gain from Revelation was really able to shine. Explosion costs an additional mana more than Revelation—and colored mana at that—and doesn’t gain any life. Explosions can act as life gain, however, if they remove a problematic permanent.
In the control mirror, Expansion is awesome. Copying an instant or sorcery for just 2 mana (with the caveat that the copied spell cost 4 or less) can give you a real mana advantage. In a counter war, it copies a hard counter and for only 2 mana helps to win any of those fights. It can also copy a removal spell that either you or your opponent happened to cast. If you’re short on mana, being able to copy a card drawing spell such as Chemister’s Insight for just 2 mana can be the difference between winning and losing.
While there’s no shortage of effects to copy, it’s important to realize just how flexible this side of Expansion // Explosion is. Whether it’s an opponent’s discard spell or maybe your own Deafening Clarion to clear out all of the bigger creatures, there’s no shortage of what Expansion can do to help you win a game.
Explosion is a game-ending spell that has effectively no use early on, but that’s where being a split card shines. When you’re short on mana, you can usually get value out of Expansion, and when you’re flooded, Explosion wins the game. These are the types of spells that offer enormous value to a Magic player.
Another Standard card that saw little play in the format just went up in value tremendously as a result of Expansion // Explosion entering the format. Azor’s Gateway never had a real impact. The ability to loot away excess lands or useless spells is a good one, and tacking that onto a card that you can slip under countermagic at just 2 mana is valuable. In the middle stages of the game, flipping the Gateway was nice, but it wasn’t game-winning. Gaining some life and a potential burst of mana was cute, but you couldn’t really do that much with Sanctum of the Sun.
Explosion plus Azor’s Gateway (or, in this case, Sanctum of the Sun) is lights out. In midrange and control matchups, it’s not uncommon to have close to 20 life, especially after you gain 5 on the Azor’s Gateway flip trigger. You combine that with your mana in play and you can Explosion your opponent clean out of the game. Should you be a little lower on life total, you can even combine Sanctum of the Sun with Teferi, Hero of Dominaria to float 10 mana untap the Sanctum during your end step with Teferi’s trigger on the stack, and get up to 20 to cast your instant! Should they happen to have infinite life, you can also target them with both targets of Explosion to deck your opponent.
Expansion // Explosion is no Sphinx’s Revelation, but in many ways it’s better. The tools are there to build some powerful control decks, and this could be just the finisher you need when opponents are prepared to deal with Teferi!