It wasn’t too long ago that straight-UR Aggro Delver was the deck I expected to fully take over the format. It was already extremely popular and putting up monster results, but a huge reason for that success was Ancestral Recall, or as the kids were calling it, Treasure Cruise.
With the banning of the big blue delve spells, Delver itself lost some luster and went back to the Temur and Grixis versions of the past. Delver of Secrets is still a busted card, however, especially in a format like Legacy where you don’t need a ton of creatures to win and can play a very low land count. Couple that with some spells that help set up the top of your library and Delver is reliably potent.
If you want to go the aggro approach, prowess creatures are exactly what you’re looking for. Monastery Swiftspear is the most powerful of the bunch thanks to the single mana cost and haste, but Stormchaser Mage’s flying means it isn’t too far behind. These can commonly attack for 3 or more damage per turn and scale nicely as all of their prowess friends will enjoy the same benefits.
Brainstorm and Ponder are two of the best draw spells in the history of Magic. They aren’t pure card advantage as they simply replace themselves, but with shuffle effects in fetchlands and Delver of Secrets to flip easily, they’re close. For a single mana, being able to tear through your deck and find the right pieces at the right time is invaluable, and with some prowess creatures, you’re dealing extra damage too.
Gitaxian Probe shows up in so many different Legacy decks for so many different reasons. That information allows you to sequence your spells properly, know what to counter, and sculpt the perfect game plan. You also get to draw a card, it’s a spell for Delver, and you get a “free” spell for your prowess creatures.
Force of Will and Daze are the perfect complements to a low-mana-curve, aggressive strategy. You have plenty of Islands to bounce and blue cards to pitch. You also don’t need all of your cards in hand since you can win the game so quickly and nothing in your deck costs more than 2 mana, so the Daze drawback isn’t crippling.
Finally, you have a bunch of burn spells to get creatures out of the way and to finish the job quickly. Lightning Bolt is the most efficient, so it’s going to always earn the 4-of slot. From there, you can mix and match. Chain Lightning is a sorcery-speed Lightning Bolt, but 3 damage for 1 mana is powerful enough that you’ll take the slight drawback.
Grim Lavamancer isn’t the fastest, but a repeatable source of damage is incredible in a number of matchups (and you can sideboard it out in the others).
Price of Progress is the highest-variance burn spell that has a huge reward. There are a number of decks that will fold to this card as 8+ damage is far too much to overcome, and there will be others that can more or less ignore it. As a 2-mana spell, this will often be your best or worst card.
Finally, there’s Fireblast, an awesome burn spell that you never want to draw 2 of since you would be very unlikely to be able to cast both.
UR Aggro Delver is a fast deck that plays out similarly to a burn deck except you get that valuable counterspell interaction with some awesome draw spells. If the “counter burn” archetype is something you identify with, this is a perfect deck to try out!