It floats at the edge of your torchlight, roughly spherical, roughly the size of a man, with what might be stalks extending from its surface. You have been staring at it for several seconds trying to decide. That may have been too long.
The Beholder Mimic — The Encounter’s Core Design #
The blast spore exists primarily as a beholder-mimic. Its entire ecology is structured around being mistaken for one of the most dangerous creatures in the RC. Understanding this is the key to running the encounter correctly.
The identification problem:
- In dim light (standard dungeon torch conditions beyond 20 ft): 10% chance to identify as blast spore (not beholder) on a d100 roll of 10 or lower
- Within 10 ft: 25% chance to identify as blast spore on a d100 roll of 25 or lower
- A party that correctly identifies the creature at range can make an informed decision
- A party that fails identification believes they are facing a beholder — the most threatening creature they know
What happens next depends on the party’s choice:
- Attack immediately (assuming beholder) → blast spore explodes for 6d6 damage to everyone within 20 ft
- Attempt to avoid/negotiate (beholders are intelligent) → the blast spore drifts toward them and sprays spores
- Cast spells (beholder’s reflection/anti-magic context) → depends on party decision-making
- Correctly identify and act appropriately → controlled engagement
The encounter is a trap built from player knowledge of another monster. A party that knows what beholders are — and is afraid of them — will be tempted to act decisively. Decisiveness triggers the explosion.
Core Statistics #
| Stat | Value |
|---|---|
| Hit Dice | 1d8* (1 HP fixed — always exactly 1 HP) |
| AC | 11 |
| AV | 0 |
| HR | 0 (spore spray is not a targeted attack — see mechanics) |
| FR | 0 |
| FD | 10 |
| Move | 30 ft (10 ft encounter) |
| Attacks | 1: spore spray (disease) OR explosion on damage |
| Damage | Disease (spore spray) / 6d6 (explosion) |
| No. Appearing | 1d3 (1 in lair) |
| Save As | Fighter 1 |
| Morale | 9 |
| Treasure | Nil |
| Alignment | Neutral |
| CR | 5 |
| Size | Medium (~4 ft diameter) |
| Intelligence | None (INT 0) |
| XP | 13 |
AC/AV Reasoning #
RC original is AC 9 (descending) = Ascending AC 11. The blast spore is a floating fungus — it has no meaningful armor, no muscle, no structure worth noting for combat purposes. AC 11 is the base ascending AC for an essentially unprotected creature.
The AC is largely irrelevant for two reasons:
- Any damage at all (even 1 point) triggers the explosion — the blast spore always has exactly 1 HP
- The spore spray is not a targeted attack requiring HR vs. AC — it is an area effect
AV 0 — A floating fungus. When hit, it explodes rather than taking damage.
FD 10 — The blast spore cannot be meaningfully grappled or shoved. It floats. Shoving it 5 ft accomplishes nothing except potentially moving it into a better spray position.
Skill Slots #
(2 total — 1 HD, asterisk = 1 special ability, INT 0)
| Slot | Skill / Ability | Notes |
|---|---|---|
| 1 | Explosion on Damage (innate, special) | The asterisk. Any damage of any amount causes the blast spore to detonate immediately. Full mechanics below |
| 2 | Spore Spray (innate) | The proactive attack when creatures approach within range. Not a “skill” in the conventional sense — it is a biological dispersal mechanism triggered by proximity |
The Two Threat Modes #
The blast spore has exactly two attack modes, triggered by different conditions. They are mutually exclusive in a given encounter — the blast spore either explodes or sprays, not both (the explosion prevents any subsequent spray; a spray does not trigger explosion).
Threat Mode 1 — Explosion (Triggered by Any Damage) #
Trigger: Any damage of any amount to the blast spore
Effect:
- Blast spore immediately detonates in a 20-ft radius explosion
- All creatures within 20 ft take 6d6 fire/concussive damage (DM determines damage type — the RC says “explodes” suggesting an organic pressure detonation rather than fire, but the DM may use fire if the setting’s ecology supports it)
- Save vs. Wands for half damage
- The explosion is instantaneous — the blast spore is destroyed
- The explosion does not spread spores (the RC explicitly states this) — the detonation sterilizes the fungal material
AV interaction: The explosion is a burst — AV applies. A character in plate mail (AV 6) who saves for half damage takes 3d6/2 ≈ 5 HP net after AV reduction. An unarmored character who fails saves takes full 6d6 = avg 21 HP.
What triggers the explosion:
- Any weapon attack that connects (even 1 point of damage)
- Any damaging spell (even 1 point of damage)
- Falling objects or environmental damage
- The blast spore “brushing” a weapon swung in its direction that deals damage
- Area effects that deal damage within the blast spore’s space
- A Dispel Magic does NOT trigger it (no damage) — but this has no other effect either (INT 0, no ongoing spell effects)
What does NOT trigger the explosion:
- Non-damaging touch or contact (a character reaching out and touching the surface without striking it — risky but technically safe)
- Spells that don’t deal damage (Charm Person — irrelevant; Hold Monster — irrelevant at INT 0)
- Movement into the blast spore’s space (contact itself is not damage — but this is very dangerous as the blast spore may spray)
- Detection/identification attempts from range
The friendly fire problem: The 20-ft radius explosion centered on the blast spore means anyone who attacks it in melee is within the blast radius. A Fighter who attacks at 5 ft range and deals damage is standing at the center of the explosion. They take 6d6 (save for half) with no opportunity to move first — the explosion is instantaneous upon damage.
Minimum safe attack range for explosion avoidance: 25+ ft from the blast spore (outside the 20-ft blast radius). At this range, ranged attacks or spells can be used without the attacker being in the explosion zone. Melee attack = suicide against a blast spore.
Threat Mode 2 — Spore Spray (Proactive, When Creatures Approach) #
Trigger: When creatures come within approach range — the RC implies this is the creature’s proactive attack when “approached.” DM determination of exact range; 20 ft is consistent with the spray volume (20×20×20 ft)
Effect area: A 20 ft × 20 ft × 20 ft cube extending in front of the blast spore
Resolution: Each victim in the spray area must make a Save vs. Poison:
- Failed save: Spores hit, penetrate, and begin growing — 1d6 blast spores germinate within the victim’s body
- Successful save: Spores missed or were repelled — no effect
The disease progression (failed save):
- Spores begin growing immediately inside the victim
- Death occurs in 24 hours unless Cure Disease is applied
- During the 24-hour period the victim is functional but deteriorating (the DM may impose escalating penalties: –1 to all rolls after 6 hours, –2 after 12 hours, –3 after 18 hours — not in the RC but ecologically consistent with internal fungal growth)
- At 24 hours, if untreated, the victim dies and the 1d6 new blast spores emerge from the body (fully formed, at their starting 1 HP each)
The new blast spores: Each blast spore created from a victim has the same statistics as the original — 1 HP, explosion trigger, spore spray capability, 1d3 appearing for future encounters. A single infected victim who dies creates 1d6 more blast spores. Each of those can infect multiple victims. The reproductive math is disturbing.
Cure Disease: The RC states Cure Disease removes the infection. This is a 3rd-level Cleric spell. The victim must be treated within 24 hours of infection. After death, Cure Disease cannot reverse the outcome — the body is the growth medium, and reversing death requires Raise Dead (if any remains are left after the spores emerge).
Spore spray does not cause explosion: The blast spore survives using the spore spray — it is still alive at 1 HP afterward. It can spray again if creatures are still within range next round (or the DM may rule the spray is a one-time biological event per encounter — the RC doesn’t clarify frequency).
Identification Mechanic — Full Procedure #
Step 1 — Initial sighting (beyond 10 ft): The party sees a floating sphere in dim light. Unless a party member specifically states they are examining it critically, the DM should present it as appearing to be a beholder.
Roll d100 for any party member who looks at it:
- 01–10: Identify as blast spore (not beholder)
- 11–100: Cannot tell the difference (it looks like a beholder)
Step 2 — Close examination (within 10 ft): If the party approaches to within 10 ft without triggering the explosion: Roll d100 for any party member who examines it closely:
- 01–25: Identify as blast spore
- 26–100: Cannot tell the difference
Modifiers to identification: The RC gives base percentages. Skills-Based BECMI modifiers:
- Nature Lore (Expert): +20% to identification chance (knowledge of unusual fungi)
- Knowledge: Monsters (Skilled+): +15% to identification chance
- Bard Lore ability (INT+WIS+CHA+Level×2 vs. d100): If the Lore roll succeeds, the Bard recalls information about blast spores and identifies on sight at any range
- Previously encountered a blast spore: +30% (experience is the best identifier)
- Dim light penalty: Standard dungeon torch conditions already factored into the base percentages — brighter light (daylight, Continual Light) improves identification by +10%
- Darkness/low light below standard torch: –10%
What identification reveals: A successful identification tells the party: “That is a blast spore — a fungus that mimics beholders. Any damage causes it to explode in a 20-ft radius. Getting close may cause it to spray infectious spores.” This is exactly the information needed to make good decisions.
What a failed identification leads to: The party believes they are facing a beholder. Their responses, from most to least likely:
- Immediate ranged attack (shoot first, before the beholder can use its rays) → explosion
- Cautious approach looking for anti-magic cone (beholder tactics) → spore spray
- Attempt to flee → blast spore approaches (30 ft / 10 ft encounter), potentially triggering spray
- Call for the party’s Magic-User → Magic-User approaches, likely within spray range
Ecology — The Beholder Mimic Is Not Coincidence #
The blast spore looks like a beholder because this provides a survival advantage. In any dungeon ecosystem where beholders exist, prey animals have developed a strong avoidance response to beholder-shaped floating spheres. The blast spore exploits this avoidance — creatures that would attack a normal fungus hesitate, giving the blast spore time to spray spores.
Why Morale 9? INT 0 means the blast spore cannot “decide” anything. Morale 9 for a creature with no mind reflects that it does not flee (it cannot make the decision to flee). The Morale 9 is a DM convenience for edge cases — treat it as the blast spore always drifting toward the nearest life-form unless some external force prevents it.
Habitat (cavern and ruins): Beholders inhabit caverns and ruins. The blast spore’s mimicry works best in these environments — the places where prey animals are most likely to fear a beholder. In surface environments where beholders are unknown, the blast spore is just a strange floating fungus and loses its mimicry advantage.
No. Appearing 1d3 (1 in lair): The lair number (1) is interesting — a blast spore “lair” is wherever one is growing. The 1d3 wilderness/dungeon number means a small cluster. Encountering three blast spores simultaneously multiplies the risk: three potential explosions, three potential spray zones, and each dead character creating 1d6 more.
Reproductive chain: A single blast spore that successfully infects and kills one victim creates 1d6 new blast spores (avg 3–4). Those blast spores, over time, can infect more victims. In theory, a single blast spore encountering a party of four could create 4d6 new blast spores (avg 14) if all four are infected and none receive Cure Disease. The exponential reproduction is the ecological horror — this creature is designed to multiply.
Treasure Note #
Treasure Type: Nil — but not because there is nothing of value. The blast spore’s 1 HP and explosion trigger means any treasure near it was either:
- Carried by a victim who was sprayed and died nearby (their equipment still exists)
- Destroyed in a previous explosion
- Still on or near the victim’s body as the spores germinate
A party that successfully neutralizes a blast spore without triggering the explosion might find equipment from past victims nearby. The DM may place minor treasure (1d4 items from the equipment table, minus any that would have been destroyed by previous explosions) in the vicinity.
Encounter Notes #
The only correct response to a blast spore:
Option A — Identified correctly at range: Use ranged fire attacks from beyond 20 ft. The explosion radius is 20 ft; the attacker at 25+ ft is safe. A Fireball centered on the blast spore triggers the explosion (6d6 damage in 20 ft radius, as normal) — any party members within 20 ft of the blast spore take the 6d6 explosion damage in addition to any Fireball damage. Clear party members back before using area fire.
Option B — Identified at close range (within 20 ft) before action: Do not attack. Back away carefully to beyond 20 ft before attacking. If the blast spore begins drifting toward the party (Morale 9 → approaches life-forms), maintain distance. If it sprays before the party can retreat, the infected party members need Cure Disease within 24 hours.
Option C — Not identified (believed to be beholder): Whatever the party does, the most likely outcome is explosion or infection. The DM should not prevent this — it is the encounter’s design. A party member who identifies “wait, this thing hasn’t used any eye rays yet” after a round of hesitation may have the insight to reconsider. The 25% identification chance within 10 ft provides a second-chance roll.
Running the identification moment: The DM should present the initial sighting neutrally: “You see a floating sphere, approximately four feet in diameter, drifting slowly toward you. It has what appear to be stalks extending from its surface.” Do not confirm or deny beholder-hood. Let the party’s own knowledge and the d100 rolls determine what they believe.
CR 5 justification despite 1 HP:
- 6d6 explosion in a 20-ft radius (avg 21 damage, save for half) to potentially the entire party simultaneously = devastating opening round
- The infection mechanic (1d6 new blast spores per killed victim) has campaign-level consequences
- The beholder-mimic identification problem means the party’s own fear of beholders makes them more dangerous to themselves
- A correctly-identified blast spore dealt with by a prepared party is trivially easy (CR 1 at most)
- An unidentified blast spore in a party of four that attacks in melee is potentially a TPK encounter
- CR 5 represents the average case where the party is partially fooled and makes one bad decision
The 24-hour clock after infection: Once a party member is infected, the encounter gains a time dimension. The party needs to find a Cleric with Cure Disease within 24 hours. In a dungeon context: retreat to the surface and find a Cleric, or have one in the party who can cast it. A party with no Cleric and no Cure Disease scroll has a genuine problem — they must get to civilization within 24 hours or lose their party member.
The new blast spores emerging from a dead character create a second encounter 24 hours later. If the infected character dies in the dungeon and the party moves on, they may return to find 1d6 blast spores where their companion fell.
