THE UNDERREALM FIELD GUIDE

Shroom and Gloom Mechanics

Know what the mechanic does before spending your next card.

Game version: Early Access / Guide updated: September 12, 2026

Combat Deck & Explore Deck

Combat cards handle battles. Explore cards help you navigate dungeons, modify cards and unlock new abilities.

How it works

Use Combat cards to handle enemies and Explore cards to get through rooms. When choosing a reward, ask which half of your run needs help.

Example

An Explore card that improves an attack can make your next fight easier. Do not judge exploration rewards only by what they do in the current room.

Common mistake

Evaluating every card only by immediate combat damage.

Card growth

Cards can grow and be modified. Their initial form is not necessarily their final form.

How it works

Both starting cards and rare cards can grow or be modified. Read the card’s growth condition: different cards improve in different ways.

Example

When comparing your upgraded attack with a screenshot, compare the full text instead of assuming that a matching name means matching damage.

Common mistake

Assuming two cards with the same name still deal the same damage after upgrades.

Eating & healing

Enemies can become recovery: the game supports eating them for health and using roasted enemies in soups.

How it works

Read each food card for its healing amount and extra effects. Before making soup, check what ingredients it uses and what you get back.

Example

Before spending a food card, compare the recovery it offers now with the other uses your current hand explicitly allows.

Common mistake

Assuming every food restores the same amount or follows a recipe from an older build.

Foresight

Each launch character has a base Foresight card that changes how they play.

How it works

Read your character’s base Foresight alongside their starting cards. A card that helps trigger it can be worth more than an isolated damage upgrade.

Example

Before building around a trigger, check the Foresight shown for the character you selected.

Common mistake

Following a Demo unlock or carry-over guide without checking whether it applies to your game. This page does not yet cover every Foresight or how to unlock it.

Rest, Warmth & Threat

Treat exploration Rest as a resource refresh with a room-dependent risk, rather than a guaranteed heal.

In the runs used for this guide, exploration Rest restores energy and cycles cards, but staying in a room can increase danger. Check the room warning before resting again; warmth and hazards affect how long you can stay.

Before you rest

  1. Have a reason to stay. Name the tool or resource you need: a dig, an unlock, a reveal or a way to use a structure.
  2. Check the warning again. Look for predicted damage and objects that change when you rest. Do not assume that the previous turn’s safe state still applies.
  3. Use relevant protection first. If a card can add warmth or address the displayed hazard, check its target and cost before refreshing your hand.
  4. Keep an exit plan. Compare the possible reward with the health and tools needed to reach the next encounter.

The exploration Rest action is different from a card named Rest. Do not assume the action heals you just because a card does.

Energy

Check a card’s current cost against your available energy before committing to a sequence of plays.

When you run out

If you cannot afford an exploration tool, Rest may let you draw or play what you need. First check whether staying is worth the danger. Read the room warning before resting.

Example

Count the total cost of your planned plays, including any changed costs. Producing a useful card does not guarantee enough energy remains to play it this turn. Recheck after each cost change.

Common mistake

Spending all your energy setting up a combo, then having none left for the finisher. Count the whole sequence before playing the first card.

Fatal, Consume, Exhaust & Linger

These keywords tell you when an extra effect triggers and what happens to a card after you use it.

Fatal

A bonus tied to a killing hit.

Use other attacks to bring a target within the intended finisher’s range. Dealing damage without killing the target does not meet the stated fatal condition. The bonus depends on the card; it is not always healing or growth.

Finishing-hit growth example →

Consume

Consume destroys the card after use.

A consumed tool may solve the current obstacle but be unavailable later. Check whether you need to preserve it for another room. Consume does not by itself mean food or healing; read the rest of the effect before using it.

Exhaust

Exhaust removes a card for the encounter rather than deleting it from your run.

Do not plan to redraw an exhausted card later in the same fight. Inspect the actual tooltip before carrying that assumption into another type of encounter. Exhaust and Consume describe different availability limits.

Linger

Linger keeps a card in your hand at the end of the turn.

Keeping one part of a combination can let you wait for its partner. This does not mean the card is free to play or immune to other removal effects; check its full text.

Also inspect limited-use counters. A battery charge, a consumable tool and an exhausted card have different implications for later encounters.

Gunk, Data & Machines

Gunk can make affected cards more expensive. Cleaning can bring the cost back down, but some cards reward adding or removing Gunk. Check which effect you want to trigger before cleaning your whole hand.

Use Data to activate a Machine. Read the Machine’s effect before choosing a target: repeating a random attack will not guarantee a hit on the enemy you want to finish.

Before taking another Machine, check whether the deck has enough activation and draw to use it. Before taking a Gunk payoff, check whether the increased cost leaves the hand playable. See the Facility build checklist.

Why won’t Data activate Splatter Saw?

This can be a game bug. A September 11 launch-period report showed Data failing on Splatter Saw, and Team Lazerbeam acknowledged the problem.

If you hit the same issue, use another playable attack or Machine instead of spending the turn looking for an unstated combo requirement. The developer’s reply promised a fix but did not identify a fixed version.

If it still happens in your build, include a screenshot of both cards when reporting the issue. This report concerns Splatter Saw; it does not mean Data fails on every Machine.

Automatic saves

The game saves after you win a fight or escape a dungeon.

Common mistake

Quitting halfway through a fight may not preserve that exact moment. Finish the encounter before relying on the autosave.

Sources & version notes

Splatter Saw report and developer reply, September 11, reviewed September 12, 2026. This establishes an acknowledged launch-period issue, not a reproduced test or a verified fix. No fixed build is stated in the reply.

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.
  • The Mushroom Roguelike Everyone’s Been Waiting For | Shroom and Gloom — 00:37–04:30; 15:11.
  • Shroom and Gloom Early Access Review - Mushroom Mayhem in a Roguelike Dungeon Deckbuilder — 02:51–04:42.
  • 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.