HOLLOW THRESHOLD 1: THE TEMPEST GATE#

Plane Connection: Material Plane ↔ Elemental Plane of Air

ARENA LAYOUT#

A 50-foot diameter circular platform of black stone floats in howling winds. Lightning crackles between three towering storm-spires (20ft tall, 5ft wide) arranged in a triangle around the center. The Tempest Egg hovers 10 feet above the platform’s center, wreathed in electrical energy. A shimmering portal to the Material Plane sits at the platform’s edge (south), while violent winds from the Air Plane tear through an unstable rift (north).

Elevation: Platform (ground level), Storm-spires (20ft), Tempest Egg (10ft above center)

ENVIRONMENTAL EFFECTS (Roll d6 each round)#

1. Lightning Surge: All creatures within 10ft of storm-spires make DC 15 Dex save or take 2d6 lightning damage
2. Gale Force: Strong winds push all flying creatures 15ft toward Air Plane portal (DC 15 Str save negates)
3. Thunder Crack: All creatures make DC 15 Con save or be stunned until end of next turn
4. Electrical Overload: Metal weapons/armor spark - wielders take 1d4 lightning damage, attacks have advantage
5. Updraft: All creatures can fly 30ft this round (hover speed)
6. Calm Eye: No environmental effects this round

SKREEK’S ARTIFACT: THE TEMPEST EGG#

Wondrous item, requires attunement

• Storm’s Fury: As a bonus action, create a 20-foot radius storm centered on you. Creatures of your choice within the area have their movement speed halved and disadvantage on ranged attacks. Lasts 1 minute. (1/long rest)
• Windwright’s Grace: You gain a permanent fly speed of 30 feet and immunity to fall damage.

ENCOUNTER#

Primary Enemies (In Arena):

• 2x Air Elementals

  • CR 5 | AC/DC 15 | HP 95 (71-119) | Atk/Prof +7 | DPR 35 | # Atks 3 | Dmg 12 (3d6 + 2)
  • Whirlwind (Recharge 4-6): 10ft radius, 30ft tall cylinder. Creatures inside: DC 15 Dex save or 3d6 bludgeoning + restrained. Whirlwind moves 30ft each turn.

• 1x Storm Herald (Modified Djinni)

  • CR 11 | AC/DC 17 | HP 165 (132-198) | Atk/Prof +9 | DPR 44 | # Atks 3 | Dmg 15 (2d8 + 6)
  • Lightning Bolt (3/day): 100ft line, DC 17 Dex save, 8d6 lightning damage. Tempest Aura: Creatures within 10ft take 1d6 lightning damage at start of their turn.

Reinforcements (1/6 chance after round 3):

• 1d4 Lightning Mephits
  • CR 1/4 | AC/DC 12 | HP 21 (17-25) | Atk/Prof +4 | DPR 7 | # Atks 2 | Dmg 4 (1d4 + 2)
  • Death Burst: When killed, explodes for 2d6 lightning damage in 10ft radius (DC 12 Dex save for half).

COLLAPSE MECHANICS#

Round 1: Portal destabilizes. Lightning strikes random locations (2d6 damage, DC 15 Dex save for half). All creatures pulled 10ft toward Air Plane portal.

Round 2: Platform cracks and tilts. DC 15 Dex save or fall prone. All creatures pulled 20ft toward Air Plane portal. Those who fail save by 5+ are pulled through and lost to the Air Plane.

HOLLOW THRESHOLD 2: THE PRECISION CHAMBER#

Plane Connection: Material Plane ↔ Mechanus

ARENA LAYOUT#

A perfect 50-foot diameter circular chamber of polished brass and silver gears. The floor is divided into concentric rings (10ft, 20ft, 30ft radii) that rotate slowly in alternating directions. Four mechanical pillars (15ft tall, 5ft wide) rise at cardinal points, each topped with a spinning gear-mechanism. The Precision Prism sits perfectly centered, rotating above a pedestal of interlocking clockwork. A stable geometric portal to the Material Plane (south) contrasts with the hypnotic gear-portal to Mechanus (north).

Elevation: Rotating rings (ground level), Gear-pillars (15ft), Precision Prism (5ft above center)

ENVIRONMENTAL EFFECTS (Roll d6 each round)#

1. Gear Shift: All rings reverse direction. Creatures on moving rings make DC 15 Dex save or fall prone
2. Clockwork Precision: All attack rolls and saving throws are made with advantage this round
3. Temporal Hiccup: Initiative order reverses for this round only
4. Mechanical Malfunction: Random pillar shoots a 30ft cone of gears (DC 15 Dex save or 2d6 slashing damage)
5. Perfect Synchronization: All creatures must move in straight lines this round or be stunned
6. Calibrated Calm: No environmental effects this round

SLUMPET’S ARTIFACT: THE PRECISION PRISM#

Wondrous item, requires attunement

• Calculated Strike: When you make an attack roll, you can choose to make it an automatic critical hit instead of rolling. The attack deals maximum damage. (1/long rest)
• Mechanical Intuition: You gain proficiency with thieves’ tools and tinker’s tools. You have advantage on Investigation checks involving mechanical devices and traps. You can cast detect magic at will, but it only detects magical mechanical devices.

ENCOUNTER#

Primary Enemies (In Arena):

• 1x Pentadrone (Modified)

  • CR 2 | AC/DC 15 | HP 52 (42-62) | Atk/Prof +5 | DPR 15 | # Atks 5 | Dmg 3 (1d6)
  • Paralysis Gas (Recharge 5-6): 30ft cone, DC 15 Con save or paralyzed for 1 minute. Repeat save at end of each turn.

• 2x Quadrones

  • CR 1 | AC/DC 13 | HP 22 (18-26) | Atk/Prof +4 | DPR 9 | # Atks 2 | Dmg 5 (1d6 + 2)
  • Precision Shots: Ranged attacks ignore half and three-quarters cover.

• 4x Monodrones

  • CR 1/8 | AC/DC 15 | HP 5 (4-6) | Atk/Prof +3 | DPR 4 | # Atks 1 | Dmg 4 (1d8)
  • Predictable: Always move toward nearest enemy in straight line. Advantage on attacks against them.

Reinforcements (1/6 chance after round 3):

• 1x Duodrone
  • CR 1/4 | AC/DC 15 | HP 11 (9-13) | Atk/Prof +4 | DPR 7 | # Atks 2 | Dmg 4 (1d6 + 1)
  • Dual Processing: Can take two separate actions on its turn.

COLLAPSE MECHANICS#

Round 1: Gears grind to a halt. All rotating rings stop. Mechanical pillars begin sparking and deal 1d6 lightning damage to creatures within 10ft.

Round 2: Chamber contracts. All creatures make DC 15 Dex save or take 3d6 bludgeoning damage as walls close in. Portal to Mechanus begins pulling creatures through (DC 15 Str save or be pulled 15ft toward portal).

HOLLOW THRESHOLD 3: THE PRIMAL HUNT#

Plane Connection: Material Plane ↔ Beastlands

ARENA LAYOUT#

A 50-foot diameter clearing of packed earth surrounded by towering primordial trees. Ancient stone cairns (10ft tall, 3ft wide) mark the cardinal directions, each carved with bestial totems. Thick roots create natural barriers and elevated platforms throughout the space. The Bloodfang Talisman rests atop a moss-covered altar at the center, pulsing with primal energy. A stone archway portal leads to the Material Plane (south), while a living tree-portal writhes with wild energy from the Beastlands (north).

Elevation: Ground level, Root platforms (5-10ft), Stone cairns (10ft), Central altar (3ft)

ENVIRONMENTAL EFFECTS (Roll d6 each round)#

1. Primal Roar: All creatures must make DC 15 Wis save or be frightened until end of next turn
2. Thorned Growth: Difficult terrain appears in 2 random 10ft squares. Creatures starting turn there take 1d4 piercing damage
3. Pack Instinct: All creatures gain advantage on attacks if an ally is within 5ft of their target
4. Territorial Marking: All creatures must make DC 15 Cha save or attack the nearest creature (including allies)
5. Savage Vigor: All creatures gain +2 to damage rolls and resistance to fear effects
6. Natural Sanctuary: No environmental effects this round

TOBY’S ARTIFACT: THE BLOODFANG TALISMAN#

Wondrous item, requires attunement

• Hunter’s Mark Enhanced: When you cast hunter’s mark, you can mark up to 3 creatures simultaneously. The spell doesn’t require concentration and lasts 1 hour.
• Primal Transformation: As a bonus action, you can assume a bestial form for 10 minutes. Gain +2 Strength, +2 Constitution, natural weapons (1d8 slashing), and 60ft darkvision. While transformed, you have advantage on Survival checks and can track by scent. (1/long rest)

ENCOUNTER#

Primary Enemies (In Arena):

• 1x Dire Wolf Pack Alpha (Modified Dire Wolf)

  • CR 2 | AC/DC 14 | HP 45 (36-54) | Atk/Prof +5 | DPR 14 | # Atks 1 | Dmg 14 (2d8 + 5)
  • Pack Leader: Allied beasts within 30ft gain +2 to attack rolls. Howl (Recharge 5-6): All creatures within 60ft make DC 15 Wis save or be frightened for 1 minute.

• 2x Dire Wolves

  • CR 1 | AC/DC 14 | HP 37 (30-44) | Atk/Prof +5 | DPR 14 | # Atks 1 | Dmg 14 (2d8 + 5)
  • Pack Tactics: Advantage on attacks if ally within 5ft of target. Pounce: If moved 20ft+ and hits, target makes DC 15 Str save or knocked prone.

• 1x Owlbear

  • CR 3 | AC/DC 13 | HP 59 (47-71) | Atk/Prof +7 | DPR 22 | # Atks 2 | Dmg 11 (1d10 + 6) + 11 (2d6 + 4)
  • Keen Sight and Smell: Advantage on Perception checks. Pounce: If moved 20ft+ and hits with claw, can make beak attack as bonus action.

Reinforcements (1/6 chance after round 3):

• 1d4 Wolves
  • CR 1/4 | AC/DC 13 | HP 11 (9-13) | Atk/Prof +4 | DPR 7 | # Atks 1 | Dmg 7 (2d4 + 2)
  • Pack Tactics: Advantage on attacks if ally within 5ft of target.

COLLAPSE MECHANICS#

Round 1: Trees begin to close in. All creatures make DC 15 Dex save or take 2d6 bludgeoning damage from falling branches. Arena size reduces to 40ft diameter.

Round 2: Primal energy surges. All creatures make DC 15 Con save or be polymorphed into a random beast (rabbit, frog, etc.) for 1 minute. Arena size reduces to 30ft diameter. Creatures touching the edge take 2d6 force damage.

HOLLOW THRESHOLD 4: THE CACOPHONY STAGE#

Plane Connection: Material Plane ↔ Pandemonium

ARENA LAYOUT#

A 50-foot diameter amphitheater of warped obsidian and twisted metal. The floor undulates in impossible curves, creating natural acoustic chambers. Four resonance crystals (12ft tall, 2ft wide) hum with chaotic frequencies at the corners, each glowing with different colored madness. The Harmony of Madness floats above a crystalline dais at the center, its music barely contained. A stable portal to the Material Plane (south) contrasts with the screaming void-portal to Pandemonium (north) that tears at sanity itself.

Elevation: Undulating floor (ground level), Crystal dais (5ft), Resonance crystals (12ft)

ENVIRONMENTAL EFFECTS (Roll d6 each round)#

1. Maddening Chorus: All creatures make DC 15 Wis save or gain 1 level of exhaustion from psychic overload
2. Sonic Shatter: All creatures make DC 15 Con save or take 2d6 thunder damage and be deafened for 1 round
3. Discordant Harmony: All spells cast this round have their effects randomized (DM’s choice)
4. Whispers of Madness: Random creature must make DC 15 Cha save or use their action to attack nearest ally
5. Euphoric Resonance: All creatures gain advantage on all rolls but take 1d6 psychic damage at start of turn
6. Blessed Silence: No environmental effects this round

SHAD’S ARTIFACT: THE HARMONY OF MADNESS#

Wondrous item, requires attunement

• Discordant Symphony: As an action, choose up to 6 creatures within 60ft. Each makes a DC 17 Wisdom save. On failure, choose their action on their next turn. On success, they’re immune to this effect for 24 hours. (1/long rest)
• Maddening Inspiration: Your Bardic Inspiration dice become d8s (or d10s if already d8s). When a creature uses your Bardic Inspiration and fails their roll, all enemies within 30ft of them must make a DC 15 Wisdom save or be charmed by you until the end of your next turn.

ENCOUNTER#

Primary Enemies (In Arena):

• 1x Howler (Modified)

  • CR 8 | AC/DC 16 | HP 90 (72-108) | Atk/Prof +8 | DPR 32 | # Atks 3 | Dmg 11 (1d8 + 7)
  • Howl of the Hunt: All creatures within 60ft make DC 16 Wis save or be frightened for 1 minute. Frightened creatures have their speed reduced to 0.

• 2x Meenlock

  • CR 2 | AC/DC 15 | HP 31 (25-37) | Atk/Prof +5 | DPR 13 | # Atks 1 | Dmg 13 (1d8 + 9)
  • Shadow Teleport: As bonus action, teleport up to 30ft to unoccupied space in dim light or darkness. Fear Aura: Creatures within 10ft make DC 13 Wis save or be frightened until start of next turn.

• 1x Chaos Beast (Modified Gibbering Mouther)

  • CR 2 | AC/DC 9 | HP 67 (54-80) | Atk/Prof +3 | DPR 17 | # Atks 5 | Dmg 4 (1d4 + 2)
  • Gibbering: Creatures within 20ft make DC 13 Wis save or can’t take reactions and must roll d10 to determine movement. Aberrant Ground: Ground within 10ft is difficult terrain.

Reinforcements (1/6 chance after round 3):

• 1d4 Quaggoth Spore Servants
  • CR 1 | AC/DC 13 | HP 45 (36-54) | Atk/Prof +5 | DPR 12 | # Atks 2 | Dmg 6 (1d6 + 3)
  • Spore Burst: When killed, releases spores in 10ft radius. DC 13 Con save or poisoned for 1 minute.

COLLAPSE MECHANICS#

Round 1: Reality fractures. All creatures make DC 15 Int save or be stunned until end of next turn as their minds struggle with impossible geometry. Resonance crystals begin emitting harmful frequencies (1d6 psychic damage to all creatures).

Round 2: Pandemonium’s winds howl through. All creatures make DC 15 Wis save or gain 1 level of madness (short-term from DMG). Portal to Pandemonium creates a 20ft radius area of extreme suction - creatures starting turn there make DC 15 Str save or be pulled 15ft toward portal and take 2d6 psychic damage.

GENERAL THRESHOLD RULES#

Closing the Threshold:

• Artifact must be retrieved from center of arena
• Character must be attuned to retrieve their specific artifact
• Once retrieved, threshold becomes unstable - collapse begins next round
• Threshold closes completely after 2 rounds of collapse

Tactical Notes:

• Elevation provides tactical advantages and cover
• Environmental effects add chaos but affect all creatures
• Reinforcements appear randomly after round 3
• Escape requires reaching the Material Plane portal before collapse completes

Scaling:

• For higher level parties: Increase monster HP by 20% and add +1 to all DCs
• For lower level parties: Decrease monster HP by 20% and reduce DCs by 1