Explorers of the Deep is one of those Commander precons that needs surprisingly little help before it starts doing something powerful.
The Lost Caverns of Ixalan deck already contains an excellent Merfolk core, several +1/+1 counter payoffs and one of the strongest typal commanders Wizards has printed in recent years. Hakbal of the Surging Soul does most of the heavy lifting himself: at the beginning of combat on your turn, every Merfolk you control explores.
If an exploring creature reveals a land, that card goes into your hand. If it reveals a nonland card, the creature gets a +1/+1 counter and you can either leave that card on top of your library or put it into your graveyard. Then, whenever Hakbal attacks, you may put a land from your hand directly onto the battlefield. If you do not, you draw a card instead.
That combination makes Hakbal unusually self-sufficient. He grows your creatures, improves future draws, keeps lands flowing and helps turn those extra lands into additional mana.
The best Explorers of the Deep upgrades therefore are not about rebuilding the deck from scratch. They are about increasing the number of meaningful Merfolk on the battlefield, getting more value from all those +1/+1 counters and making sure one removal spell or board wipe does not erase several turns of development.
Hakbal Rewards a Wide Merfolk Board
The most important resource in a Hakbal deck is not necessarily mana or even cards in hand. It is Merfolk on the battlefield when combat begins.
If you control Hakbal and four other Merfolk, you get five explore actions before attackers are declared. A nonland card can put a +1/+1 counter on one creature, then remain on top for the next Merfolk to explore. At that point you can decide again whether you want another counter and whether the card should stay or go to the graveyard.
That gives Hakbal much more control over the top of the library than the word “explore” initially suggests.
It also explains why cheap Merfolk are useful, but merely being cheap is not enough.
Cards such as Triton Shorestalker and Mist-Cloaked Herald do increase your explore count for only one mana, and being unblockable gives them a natural place to carry +1/+1 counters. But as upgrades, I would rather prioritize Merfolk that contribute something before Hakbal is even on the battlefield.
Vodalian Hexcatcher is an excellent example. It has flash, increases the power of your other Merfolk and lets you sacrifice Merfolk to tax opposing instant and sorcery spells. In a deck that can build a large board quickly, that ability gives you a way to protect the very engine you are developing.
Tishana’s Tidebinder approaches interaction differently. It gives the deck another Merfolk at instant speed while answering an important activated or triggered ability.
The point is not simply to reduce the mana curve. It is to make sure more of your low-cost creatures remain useful after turn three.
The Precon Already Contains Most of the Engine
Explorers of the Deep has one of the better stock shells among Commander precons.
Hardened Scales increases the counters generated when your Merfolk explore. Branching Evolution pushes that even further. Deeproot Elite rewards additional Merfolk entering the battlefield, while Herald of Secret Streams can make creatures with +1/+1 counters unblockable.
Then there are cards such as Kindred Discovery, Svyelun of Sea and Sky, Kumena, Tyrant of Orazca and Reflections of Littjara, all of which give the deck ways to turn a large Merfolk board into additional resources.
That means I would be careful about removing slower cards simply because they cost four or five mana.
Deeproot Historian, for example, is certainly not one of the most efficient cards in the deck, but it does something relevant with the extra lands Hakbal tends to put into your hand by giving your Merfolk cards retrace. It is a reasonable eventual cut if you want to streamline the list, but it is not fundamentally fighting the strategy.
Curse of the Swine is another card I would not remove just because it is a sorcery. Hakbal decks can develop enormous boards, but Commander still requires answers. Exiling several problematic creatures at once can be much more valuable than adding another small Merfolk.
The same applies to Ravenform. There are more efficient interaction spells available, so it is a reasonable upgrade slot, but the problem is its efficiency rather than the fact that Hakbal somehow cannot afford to cast sorceries.
A better version of Explorers of the Deep still needs interaction.
Counter Payoffs Are Where Hakbal Gets Dangerous
Because every nonland explore can add a +1/+1 counter, Hakbal does not need much help creating large creatures.
What he benefits from most are cards that turn those counters into something other than additional power.
Herald of Secret Streams, already in the precon, is perhaps the clearest example. Once most of your Merfolk have counters, Herald can turn a crowded battlefield into an attack opponents simply cannot block.
Danny Pink offers a different payoff. His ability can turn counters being placed on your creatures into additional card draw, giving the deck another reason to spread counters across the battlefield instead of building one enormous threat.
Ozolith, the Shattered Spire is another efficient counter engine. It increases the number of +1/+1 counters you put on your creatures while also giving you a mana sink when you have spare resources.
And then there is Roaming Throne.
Choosing Merfolk gives you another member of the creature type while amplifying triggered abilities from your Merfolk. That is especially powerful with Hakbal because his beginning-of-combat ability is the central engine of the entire deck. It also interacts with many of the other triggered abilities spread throughout the list.
It is a more expensive upgrade, but unlike a generic large creature, it directly increases the output of cards you already want to play.
Evasion Matters More Than Another Giant Creature
Hakbal can make Merfolk large very quickly. The next challenge is making sure those creatures actually connect.
Fortunately, the stock list already contains Herald of Secret Streams and Thassa, God of the Sea, giving the deck ways to bypass blockers.
This is also where Lord of Atlantis becomes interesting. It gives other Merfolk +1/+1 and islandwalk, adding another cheap lord to a deck that already contains Master of the Pearl Trident, Merfolk Sovereign and Merfolk Mistbinder.
I would not describe Lord of Atlantis as mandatory, however.
Islandwalk only matters when the defending player controls an Island, and unlike some newer typal lords, Lord of Atlantis affects other Merfolk, not only yours. That can occasionally matter against another Merfolk player.
It is still a strong addition, particularly if your local games contain plenty of blue decks, but Hakbal already has more reliable ways to create difficult combat.
The larger lesson is that another 10/10 Merfolk is rarely what this deck is missing. Once your explore engine is running, power comes naturally. Evasion, protection and cards that preserve your board tend to be more valuable.
Protect the Board You Spent Three Turns Building
This is the part of the stock precon I would strengthen most aggressively.
Hakbal encourages you to put many creatures onto the battlefield, and that creates the classic typal-deck problem: one board wipe can undo an enormous amount of work.
The precon already includes Inspiring Call, which is particularly good here because your creatures naturally accumulate +1/+1 counters. Giving those creatures indestructible while drawing cards can turn an opponent’s sweeper into one of the strongest plays in your hand.
Ripples of Potential, another stock card, similarly rewards having counters spread throughout the board.
Adding more cheap protection can make the deck substantially more consistent.
Heroic Intervention remains one of the cleanest options in green. Tamiyo’s Safekeeping is narrower but much cheaper if protecting Hakbal or another key permanent is the priority.
Countermagic also becomes more attractive when your battlefield is already ahead. Once you have six or seven growing Merfolk, you do not necessarily need another creature. Sometimes the best card in your hand is simply the one that prevents Farewell or another sweeper from resolving.
That is another reason Vodalian Hexcatcher is such a natural upgrade.
Some of the Easiest Cuts Are in the Mana Package
Commander’s Sphere is still one of the first cards I would consider replacing.
Three mana for a rock that produces one mana is not disastrous, and sacrificing it for a card eventually gives it some utility. But green gives Hakbal access to more efficient ways to develop mana, while his attack trigger already helps put additional lands onto the battlefield.
Replacing it with cheaper ramp makes it easier to cast Hakbal and still develop another Merfolk around the same stage of the game.
Temple of the False God is an even cleaner cut. It does nothing until you already control enough lands, which makes opening hands containing it unnecessarily awkward.
Temple of Mystery is less offensive. Scry is useful in a deck whose commander cares about the top of the library, so I would not treat it as an emergency replacement. Still, if you are optimizing the mana base, reducing lands that always enter tapped will improve the deck’s early development.
The stock list already gives you Hinterland Harbor, Vineglimmer Snarl, Secluded Courtyard, Unclaimed Territory and Command Tower, so improving the remaining slots does not require rebuilding all of your lands.
If you want to go further, our Mana Base Upgrade Guide explains how to replace slower precon lands without immediately jumping to an expensive fetchland package.
What I Would Upgrade First
I would resist the temptation to replace twenty cards at once.
The stock deck already contains Hardened Scales, Branching Evolution, Kindred Discovery, Herald of Secret Streams, Kumena, Tyrant of Orazca, Svyelun of Sea and Sky and several Merfolk lords.
That is an excellent foundation.
The first upgrades should make that foundation more reliable.
Add Vodalian Hexcatcher for interaction and protection. Add Tishana’s Tidebinder if you want another reactive Merfolk. Consider Lord of Atlantis if another cheap lord fits your table. Add a counter payoff such as The Ozolith or Ozolith, the Shattered Spire if you want to lean further into the +1/+1 counter side of the deck.
At a larger budget, Roaming Throne is exactly the kind of card worth paying more for because it strengthens the engine instead of merely providing another standalone threat.
Then spend the remaining slots on protection and cleaner mana.
Hakbal will supply the power.
PreconForge Verdict
Explorers of the Deep is already much closer to a finished Commander deck than many precons.
The stock list contains good Merfolk, real interaction, counter multipliers, card advantage and several ways to make a growing army difficult to block. Hakbal of the Surging Soul then ties those pieces together by turning every combat into card selection, additional +1/+1 counters and potentially another land entering the battlefield.
That is why the best upgrade path is not simply to make the deck faster.
Keep the Merfolk count high, but make those Merfolk useful. Turn the counters Hakbal creates into cards, protection or evasion. Replace the least efficient mana pieces. Most importantly, give yourself enough ways to protect the board once several turns of exploring have turned a collection of small creatures into a genuine threat.
You do not need to make every Merfolk unblockable on turn two.
You need to make sure the army Hakbal builds is still there when it is finally time to attack for lethal.
