Yrthak - Dungeons on Automatic Bestiary

Magical Beast · SM +3 Yrthak [Monster Manual, page 262]

Attributes

ST36

DX12

IQ9

HT13

HP36

Will11

Per11

FP15

Basic Speed6.25

Basic Move4

Dodge9

DR3

Melee attacks

Usage	Level	Damage	Reach
Sharp ClawsSharp Claws (14): thrust 4d+2 cutting (KYOS: 6d+1 cutting), Reach C-2. Can only use claws when flying.	14	thrust 4d+2 cutting (KYOS: 6d+1 cutting)	C-2
Sharp TeethSharp Teeth (14): thrust 4d+2 cutting (KYOS: 6d+1 cutting), Reach C.	14	thrust 4d+2 cutting (KYOS: 6d+1 cutting)	C
Sonic LanceSonic Lance (14): Once per 5 seconds, a yrthak can focus sonic enery in a ray. This is a ranged attack with Acc 3 and Range 10/100 that costs 1 FP. The ray deals 4d burning non-incendiary damage. The attack produces an explosion at the point of impact (on a miss, check for scatter; see p. B414). The target takes damage normally; anything nearby receives “collateral damage” equal to basic damage divided by (3 x distance in yards from the blast). If the attack hits the ground, a large rock, a stone wall, or the like, it creates an explosion of shattered stone. Everyone within 5 yards is attacked with effective skill 15, modified by range penalties from the point of impact; see Fragmentation Damage (p. B414). The fragments deal 1d large piercing damage.	14	Once per 5 seconds, a yrthak can focus sonic enery in a ray. This is a ranged attack with Acc 3 and Range 10/100 that costs 1 FP. The ray deals 4d burning non-incendiary damage. The attack produces an explosion at the point of impact (on a miss, check for scatter; see p. B414). The target takes damage normally; anything nearby receives “collateral damage” equal to basic damage divided by (3 x distance in yards from the blast). If the attack hits the ground, a large rock, a stone wall, or the like, it creates an explosion of shattered stone. Everyone within 5 yards is attacked with effective skill 15, modified by range penalties from the point of impact; see Fragmentation Damage (p. B414). The fragments deal 1d large piercing damage	—

Traits (11)

Acute Hearing 3
Bestial
Blindness
Born Biter 1
Extended Lifespan 1
Flight (Cannot Hover; Winged)
Foot Manipulators
Injury Tolerance (No Eyes)
No Fine Manipulators
Sonar (Accessibility, In air; Biological (Passive); Increased Range, 10x; Restricted Arc, 60°; Targeting)
Vulnerability (Sonic, x2)

Skills (2)

14Brawling
14Innate Attack (Beam)

Notes

GCS ancestry draft: gcs/yrthak.gct
Source template total: 121 points.
Library-rebuilt template total: 121 points.
CER was computed from parsed Typical Stats using the Dungeons On Automatic baseline CER path.
Review attacks, special abilities, encounter frequency, treasure, grappling, and GCS modifiers before approval.
Length 20 feet. Weight 5,000 lbs.

Encounter rating

CER66

Offense31

Protection35

Threat tiermajor

Appearing1

Wandering2

GCS v5 downloads

Where this one came from

Source record: Yrthak [Monster Manual, page 262]
Source system: gurps_4e_fan_conversion / author_permission
Released under: cc_by_4_0
Conversion: 0.2.0-reviewed
Review status: approved
Credit: Original GURPS conversion by Enraged Eggplant, from Monsters (May 11, 2024); adapted and republished with permission.

GCS ancestry draft: gcs/yrthak.gct
Source template total: 121 points.
Library-rebuilt template total: 121 points.
CER was computed from parsed Typical Stats using the Dungeons On Automatic baseline CER path.
CER recomputed from the reviewed Typical Stats through the canonical Dungeons on Automatic CER path: OR 31, PR 35, CER 66, threat tier major.
Conversion baseline reported OR 35, PR 35, CER 70 (tier major). The reviewed values come from the consumer CER implementation, which rounds damage once after the damage-type multiplier and credits ranged accuracy; the conversion baseline ceilinged the damage base first and ignored range.
Encounter metadata derived (gregarious): average number appearing 1, wandering weight 2. Encounter metadata derived for 0.2.0 from the reviewed threat tier and creature class (appearing: minor 4 / standard 2 / major 1 / severe 1, forced to 1 for solitary classes — including swarms, which are a single multi-body creature — and raised to 6 for gregarious minor creatures; wandering weight: minor 4 / standard 3 / major 2 / severe 1). The fan-conversion source states no appearing-in-numbers or wandering values, so these are derived, not source mechanics.
Lair, treasure, and grappling remain unpopulated in 0.2.0 by package policy: the authorized fan-conversion source states no lair, treasure, or grappling values, and review declines to invent them. See review/policy/0.2.0-empty-field-policy.md.
Review approved by automated-mechanical-review on 2026-07-26 (batch ee-2026-07-26-b4-special-mechanics); GCS fidelity check passed, DOA playability check passed.
Special-mechanics record. Mechanics the CER path cannot price are named per record in review/reports/cer-audit.md rather than folded into the number, and encounter counts are capped where a save-or-disable attack is present.

Enraged Eggplant GURPS monster conversions; used, adapted, and republished with unrestricted permission from the author. Portrait and tokens are AI-generated original art. Sources and credits.