THE UNDERREALM FIELD GUIDE

Shroom and Gloom Builds

Build around what your cards actually do. Start with a plan for damage and a plan for recovery.

Game version: Early Access / Guide updated: September 11, 2026

Try a specific combo

Concerned Parent: turn Photo’s draw into Rage →

Follow the order from Parental Instinct to Photo to an attack, with a worked damage example from the official August preview.

01 / DAMAGE PLAN

Grow a reliable attack

Pick an attack you can use consistently, then choose upgrades that help it do its job. A powerful finisher still needs a plan for the turns when you do not draw it.

Look for
Growth conditions you can actually trigger with your current deck.
Potential advantage
A clear purpose for your upgrade choices.
Trade-off to check
Can you still handle a hand that does not contain the upgraded attack?
Use this approach when
Your deck already supports the card’s condition, without needing a card you have not found yet.
Understand card growth →
02 / RECOVERY PLAN

Make food part of the plan

Food can keep a run alive. Look for ways to make it during combat, then weigh healing against any bonuses you get from eating.

Look for
Cards in your actual hand that produce or use food.
Potential advantage
A plan for sustaining health through a run.
Trade-off to check
Does preparing recovery prevent you from dealing with the current threat?
Use this approach when
Your current card text supports the food interaction you intend to use.
Understand eating →

Check a combo before committing

  1. Read the trigger. Make sure you understand what must happen before the effect resolves.
  2. Count the required resources. Use current in-game costs, including any modifications.
  3. Check the target. Check whether the card hits one enemy, several enemies, or buffs you.
  4. Consider the fallback. Decide what you will do if one part of the combination is unavailable.

What about character builds?

Each character starts with different decks and a base Foresight. Use those starting tools to guide your picks. Meet the characters →

Which build should I aim for?

There is no single deck list recommended here for every run. Use these three approaches to choose cards you can actually find and play together.

Pattern: give growth cards the finishing blow

If your Hungry Blade grows on a fatal hit, use smaller attacks to set up its kills. Do not sacrifice too much health just to gain another upgrade.

  • Setup: use other attacks to put an enemy within the finisher’s current damage range.
  • Payoff: land the finishing hit with the growth card when the incoming damage makes that safe.
  • Failure case: delaying a kill for growth may cost more health than the upgrade is worth. A deck also needs a plan for turns when the finisher is not drawn.

Prioritize enough usable attacks to control the fight. Add draw or upgrades to support an existing plan, rather than depending on a future reward to make it function.

Pattern: connect food production to eating rewards

If Roast makes food and your other cards reward eating, use them together. Check the exact trigger: producing food, drawing it and eating it are different actions.

  1. Establish a dependable way to produce food.
  2. Check the eating payoff and whether it is active when you consume that food.
  3. Count energy and draw as well as damage: extra cards do little if you cannot play them.
  4. Keep enough recovery to survive a hand that does not assemble the loop.

Food can also have exploration uses. If your hand allows feeding a creature or trading with a merchant, compare that opportunity with immediate healing. Do not assume every merchant takes food.

Pattern: support Machines with Data and cleaning

A Machine deck needs useful Machines, enough Data to activate them, and a way to manage Gunk costs. Adding more Machines will not help if you cannot trigger the ones already in hand.

  • Machine support: if Employee Handbook can trigger your turret, use it when another attack will help. Check that the Machine is an eligible target and that repeating its effect addresses the current enemies.
  • Cleaning support: use Sweep on a Gunk-covered card when cleaning makes it affordable. Inspect whether cleaning first improves your actual hand or consumes a resource you need elsewhere.
  • Fallback: avoid a hand full of activation cards with no Machine available, or expensive Gunk payoffs with no way to clean them.

Keep the deck playable even when you draw its pieces in the wrong order. Add another activation card only when you have enough Machines to use it.

Sources & version notes

Last verified against the sources below: . This is a source check, not an in-game test of every interaction. Unconfirmed details are labelled separately.

Gameplay transcript sources

Original summaries based on editor-supplied YouTube transcripts. Video URLs, recording dates and build IDs were not included; footage has not been independently checked. Titles and timestamps identify the supplied excerpts.

  • I’ve Been Waiting YEARS for this Roguelike — 03:26–05:36; 08:29–11:24; 12:33–15:16; 19:12–19:38; 1:13:50–1:22:00.
  • I CLEANED The FACILITY with GUNK & MACHINES in this Double Deckbuilder! - Shroom and Gloom — 02:26–05:14; 18:09–20:15; 25:31; 38:12–39:37.