The Atomic Unit of a Build: Conversion Chains

Neon Abyss 2 has no cap on how many items you can carry, but almost no single item makes you stronger on its own. What strong items actually do is convert resource A into resource B. A build takes shape as the set of conversion chains you switch on during a run. Start by learning the resource board:

Resource	Where it comes from	Where it goes
Coins	Room-clear rewards, boss drops (enemies barely drop coins)	Shops, the Recolor Machine, loan repayments
Crystals	Room drops, chests	Fueling Curio effects
Keys / Bombs	Room drops, chests, shops	Opening doors, blowing up walls, triggering explosion mechanics
Eggs	Wooden crates and vases, room rewards, chests, shopping shrines	Hatching Hatchmon
Faith	Built up over a run (see /systems/faith)	Triggering Faith effects, powering Faith-scaling items
Soul Shards	Boss drops, Vaporized weapons	Weapon upgrades, rolling affixes
Weapons	Room and chest drops	Used directly, or Vaporized for resources

Published conversion items chain together cleanly:

• Blackbrew: spend 2 Crystals → gain a bomb (Crystals into bombs).
• Firecracker: +2 Bombs, and thrown bombs can drop chests (bombs back into items and coins).
• Cosmic Pouch: consumes Crystals to vacuum nearby drops, then generates an Artifact after collecting enough (Crystals plus stray drops into Artifacts).
• Kane's Cube: consumes Crystals to convert Relics in the room into Artifacts (Relics into Artifacts).
• Philosopher's Stone: changes Extraction to grant a random Artifact instead (Extraction into Artifacts).
• Vaporizing weapons: breaks unused weapons into Soul Shards and other currency, feeding upgrades for your main weapon.

A chain only works if it has both a source and a sink. Blackbrew with no Firecracker and no cracked walls to blow open just turns Crystals into dead weight. Before picking up a conversion item, ask two questions: do I have enough of the input to feed it, and do I have somewhere to spend the output?

Every item drops at most once per run

Each item can drop only once in a given run, and same-type bonuses stack additively (damage is computed as your largest single category bonus plus generic damage bonuses; crits are a fixed ×2). That means spreading out across several small pieces of the same type usually comes together faster than saving up for one big one — and on conversion chains it matters doubly, because any single link may never appear again. When you see a link, take it.

How the Five Categories Feed Each Other

Items come in five categories (detailed in /systems/items). From a build-planning perspective, each category has a job:

Category	Role in a build	Representative items and what they feed
Curios	Engines of conversion chains	Cosmic Pouch (Crystals → Artifacts), Kane's Cube (Relics → Artifacts), Express Box (packs up room items to take with you)
Artifacts	The stat chassis and multipliers	Squid Brooch (coin thresholds into damage), Ghost Proxy (move speed into attack speed), Purity Sigil (Faith into damage)
Relics	Rewrite the rules of the run	Philosopher's Stone (changes Extraction), Empty Cup (stops weapon leveling while keeping upgrade areas open)
Hexjars	Long-horizon investment containers	Charged with weapon EXP, Faith, and other resources — the longer they brew, the more they pay out
Oddities	High-variance wildcards	Goose (getting hurt summons attacking geese), Goblin Chest (may duplicate your items or confiscate them)

Three sentences cover the feeding relationships: Curios create new resources, Artifacts amplify the ones you already have, and Relics redirect the flow of the entire board. A finished build usually has all three layers — a Relic sets the direction, Curios supply raw material, and Artifacts turn it into numbers.

Five Signature Builds

Coin Build: Your Wallet Is the Weapon

• Core items: Squid Brooch (−10% damage under 100 coins, +30% damage over 300) and Firecracker (+2 Bombs; thrown bombs can drop chests, a steady source of coins and items).
• What it needs to come online: a reliable coin income early. Since coins come mainly from room clears and bosses, the coin build demands that you clear rooms fast and get hit rarely to snowball. Blackbrew converts idle Crystals into bombs, and Firecracker turns those bombs into chests.
• Power spike: smooth all game, strongest in the mid game (floors 3–4) when shop refreshes are frequent and you can buy whatever shows up.
• Weakness: famine. If coins drop below 100, Squid Brooch turns on you for −10% damage and the snowball becomes an avalanche. Shop items run about 70 coins — spend within your means and don't empty your health bar to afford a big piece.

Hatchmon Build: Eggs Are Productivity

• Core items: Tenacious Sapling (downed Hatchmon revive on their own) and Dinosaur Skull (explosions also build hatch progress). Agent Elise is the natural pick: her exclusive Hatchmon Kiddy follows her permanently, can't be fused away, and is effectively a free permanent fighter.
• What it needs to come online: dense egg income — smash wooden crates and vases religiously and clear shopping shrines as you pass. Four specific mini Hatchmon in the right combination fuse on the spot into a Super Hatchmon, and the Recolor Machine (pay coins to repaint an egg) lets you force the combinations you need.
• Power spike: mid to late game. Hatching and fusing both take runs of accumulation, so early combat is thin — but once assembled you field multiple auto-aiming attack squads that deal damage even while you stand still.
• Weakness: slow to assemble and vulnerable to rushdown. Weak room clearing early starves the rest of your resource board, some Super Hatchmon actually attack less eagerly than their components, and fusion results can't be chosen manually — there is real "fused into the wrong thing" variance.

Melee Build: Trade Range for Tempo

• Core items: Ghost Proxy (+20% move speed, and half of all speed bonuses also apply to attack speed) — on a melee weapon you fight in melee range, so attack speed is everything. Frenzy-type bonuses (one rank per 4 stacks, up to +50% damage) reward exactly the aggressive positioning melee demands.
• What it needs to come online: a melee weapon that feels good on floor 1 and a disciplined dodge rhythm. Both Frenzy and melee payoffs assume you rarely get hit — taking a hit costs you Frenzy stacks.
• Power spike: strongest early and mid game. Point-blank room clearing is fast, and fast clears accelerate every other resource chain in your build.
• Weakness: late-game tolerance collapses. Hits on floors 1–4 cost half a heart; from floor 5 onward every hit costs a full heart, so each melee-range mistake is twice as punishing. Dense bullet-hell boss fights are the hardest matchup.

Summon Build: Let Someone Else Shoot

• Core items: Goose (getting hurt summons a flock of attacking geese). Wisps — soul flames — are a separate, pickable resource class alongside the set mechanic, and Wisp-related items form the second leg of the summon build.
• What it needs to come online: after the first summon source (geese, Wisp items), deliberately collect "on-hit payoff" and "summon buff" pieces until summons stop being a bonus and become your main damage.
• Power spike: mid to late game. As enemy density rises, auto-aiming summons soak up huge amounts of bullet pressure and you only have to dodge.
• Weakness: Veewo has not published complete summon damage numbers or a full Wisp item list, so the build leans heavily on what actually drops in your run. Summon damage per investment usually trails direct-damage builds, and high-HP single-target bosses expose the gap — expect to chip.

Faith Build: Faith as a Fixed Deposit

• Core items: Purity Sigil (damage scales with Faith; at full Faith gain +1 projectile). Each Faith — Consumerism, Agapeism, Artisanism, and the others (see /systems/faith) — comes with its own directional bonuses, so choosing a Faith is choosing a build line.
• What it needs to come online: commit to a direction early and keep donating. Faith accumulates over the whole run, so switching mid-run sinks everything you invested.
• Power spike: late game. A full Faith bar turns Purity Sigil's bonus projectile into a qualitative jump for any damage source, and stocked-up Faith can be spent at key moments to swing a fight.
• Weakness: long vacuum. Early and mid game you effectively run one Artifact short, and charge-up Hexjars like Candle Jar compete with Faith-scaling items for the same resource — plan the split in advance.

Which Line Do You Commit To? A Decision Path

You don't need to pick an archetype at the start. Read the run in this order:

1. Floor 1, check your weapon. A melee weapon that feels great points at the melee build. If neither ranged option feels right, look at summon or Hatchmon lines that don't depend on your own aim.
2. Floor 1, check your Faith options. Faith is a no-refund, full-run investment — pick a direction on floor 1 and align everything after it (Hatchmon build leans Agapeism; coin build leans Consumerism).
3. Floor 2, count categories. Holding 8 items of the same category grants that category's set bonus for free (pocket slots don't count). Whichever category the drops favor, complete that conversion chain.
4. Floor 3, read the shop. Shops on floors 1–3 always stock health/shield (about 20 coins), one item (about 70 coins), and one weapon (about 50 coins); floor 4 adds a Curio slot. Whether you can afford the key link in your chain is the direct test of whether this run wants you farming or rushing.
5. All run long, ask three questions. Where does my resource come from? What does it convert into? Where is the exit? If you can't answer all three for a chain, skip its items and save the slot and budget for your main line.

Builds can pivot — Faith can't

Mid-game pivots like "melee into summon" or "coin into Hatchmon" are fine as long as the new chain's source item shows up — the sunk cost of the old chain is acceptable. The only things that can't pivot are Faith and Relic-scale rule changes, because they alter the foundation of the entire run.

Sources

• Neon Abyss 2 on Steam: official line on limitless item synergy, the Hatchmon system, and 4-player co-op.
• Neon Abyss 2 — Nintendo Switch store page: official description of unlimited item carrying and Hatchmon hatching and evolution.
• Neon Abyss 2 Items and Synergies — Neon Abyss 2 Wiki: verbatim published effects for Curios, Artifacts, Relics, Hexjars, and Oddities, including Squid Brooch, Ghost Proxy, Blackbrew, and Firecracker.
• Neon Abyss 2 :: Glimmer Heist update announcement — Steam: official patch-note text for Cosmic Pouch, Kane's Cube, and other conversion items.
• CapyDB Neon Abyss 2 mechanics guide: damage formula, Frenzy ranks, the 8-item set trigger, shop pricing, and the once-per-run item rule.
• Veewo Games early access launch press release (GamesPress): the 400+ item count at early access and the "faster, riskier, limitless" design direction.
• TheGamer: hands-on writeups covering the five base Hatchmon, evolution tiers, and the four-mini fusion rule into Super Hatchmon.