Mono Blue Delver is the most powerful budget deck in Modern that nobody is playing!

Monoblue Delver finally has all the tools it needs to be a competitive deck in Modern now, and it’s the single best budget deck in the format imo.

Here is a sample list..

17 Island

4 Delver of Secrets
4 Pteramander
3 Cryptic Serpent

4 Thought Scour
4 Opt
4 Serum Visions

3 Spell Pierce
3 Spell Snare
3 Remand
2 Mana Leak
1 Disrupting Shoal

3 Dismember
3 Vapor Snag
1 Repeal
1 Psionic Blast

The list above is different from UR aggro lists in a number of key ways. It plays a much lower curve. This allows it to function off of just 17 lands and draw business more consistently, but also means the curve is too low to support numerous Snapcasters, Nimble Obstructionists or Vendilion Cliques. Although including any of these cards in your variant wouldn't be wrong, as long as you keep the total number of 3cc spells to under 4.

It plays a record number of conditional counterspells. This is why you absolutely never want to tap out on your turn until the midgame (to play a threat that will close out the game in a couple of turns). This is why it plays zero sorceries and zero Thing in the Ice. You want to only play your cantrips at the end of your opponents turn once you're certain that they haven't played anything that you want to counter or bounce or dismember. Thought Scour is an amazing card here. It routinely functions as a Dark Ritual with a cantrip attached to it. The rest of the list is self explanatory.

Any questions or feedback is welcome.

I feel that Serum Visions is not needed at 4 slots, maybe 2. I've played a lot of UR Wizards and I only play 2 copies in that deck (alongside 4x Opt.) With Scour and Opt, SV is actually the worst cantrip. Having 10 is probably necessary given only 17 lands, but Serum is the worst of the bunch at supporting the plan.

The problem with Disrupting Shoal is that you need a decent curve to make it work. My experience with the card in both Modern and Legacy is that it is often just a free Spell Snare, which is a bad deal when you could just play actual Spell Snare. The Phantasmal Bear/Spellstutter Sprite/Ninja of the Deep Hours deck played 4x Ninja and 4x Cryptic Command so it could counter opposing Cryptics, Scapeshift, etc. I don't think the Shoal is worth any slots. You could easily get away with a misers Cryptic Command if you upped the land count to 18. Spell Pierce is also a little lackluster in the format, I wouldn't play 3 copies. Swap out 1-2 with Dispel, which is surprisingly good at winning counter wars or just cheaply protecting your threats. Abrupt Decay is rare in the format now, it sees play only in Jund/Rock, and even there it's mostly in the sideboard. Assassin's Trophy has taken over (which is good news for this deck!) Another very good counterspell in Modern, that nobody plays, is Deprive. Once you get to land #3 playing a Deprive doesn't even bother you. I played it in Jeskai Delver a bunch, usually 2 copies. It's very good.

Now for the real issue: other than budget, you lose literally *nothing* by splashing red, but you get a significant amount of upgrades. Lightning Bolt is still the best red card in the format, Bolt - Snap - Bolt is still incredible, and Young Pyromancer, Grim Lavamancer, Monestary Swiftspear are all very good threats that diversify the approach.

Here are some general suggestions:

-2 Serum Visions
-1 Disrupting Shoal
-2 Spell Pierce

+1 Land (probably Ghost Quarter x1)
+1 Dispel
+1 Vapor Snag (play a 4/2 split of Snag/Dismember. Maybe the other 2 Dismembers in the sideboard.)
+2 Deprive

As you noted, conditional counterspells are sometimes unreliable. Playing a couple Deprive means you will always have a couple hard counters in your deck. Repeal and Psionic Blast are a little weird as well. The reach from Blast seems good, so maybe 2x Blast and cut the Repeal.

Here are some cards to consider for your sideboard:

Entrancing Melody (Death's Shadow, Tarmogoyf, Goblin Guide, etc.)
Disdainful Stroke (Tron, Eldrazi, UWx control, Scapeshift, TitanShift)
Ceremonious Rejection (Tron, Eldrazi, Affinity)
Echoing Truth (random nonsense)
Threads of Disloyalty (Shadow, Goyf, Goblin Guide, same as Melody it just doesn't scale up)
Ratchet Bomb (tokens, Humans)
Pithing Needle (Jace, Liliana, other PW's)
Phyrexian Revoker (same as Needle but attacks for 2)
Aetherize (it's a little steep at 4 mana, but it's instant and it can win races against aggressive decks)
Tormod's Crypt (only hits opponent's graveyard)
Grafdigger's Cage (you aren't playing Snapcasters, so it's a free roll)
Damping Sphere (storm, tron)

Also, with an all Island mana-base I think Tempest Djinn becomes really appealing, probably better than Cryptic Serpent due to evasion. It still serves to make land-flood hurt less, just like Pteramander/Serpent, but isn't dependant on the graveyard.

I'd probably do this:

4x Delver
4x Pteramander
2x Cryptic Serpent
2x Tempest Djinn

We haven't even started talking about Sphinx of Foresight yet, which I think could also be very good, even with only 18 lands.

Peek