It would be ridiculous to try and out-do what Sean K. Reynolds has already brilliantly done for D&D 3.5 in The New Argonauts so at the start of every one of these posts I’m going to 1) thank him for making that supplement (thank you Sean!) and 2) tell you to go download it (it’s free–give it 5 stars because damn). This blog series is not intended to be a reproduction of that product, only a conversion update. Go get it.

Post 1: What You Need To Play

Master Page for D&D 5E Ancient Greece/Monster List

Geryon

Large giant, neutral
Armor Class 16 (breastplate, shield)
Hit Points 210 (20d10+100)
Speed 35 ft.

Saving Throws Con +8, Dex +3, Cha +4
Skills Animal Handling +5, Investigation +3, Perception +5, Persuasion +4, Religion +3
Senses passive Perception 20
Languages Common
Challenge 8 (3,900 XP)

Ageless. Geryon cannot suffer from frailty of old age, die from old age, or be aged magically.
Power Attack. When Geryon makes his first melee weapon attack in a turn, he can choose to take a -5 penalty to his melee weapon attack rolls in exchange for a +10 bonus to melee weapon damage. In addition, Geryon can use a bonus action to make one melee weapon attack after he uses a melee weapon to reduce a creature to 0 hit points or scores a critical hit with it. Geryon can only use this feature on his turn.
Three Heads. Geryon gains double his proficiency bonus to and has advantage on Wisdom (Perception) checks. In addition, he has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, or knocked unconscious.

ACTIONS
Multiattack. Geryon attacks three times.
Greatsword. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 14 (2d8+5) slashing damage.
Javelin. Ranged Weapon Attack: +8 to hit, range 30/120 ft., one target. Hit: 9 (1d8+5) piercing damage.

Geryon was the monstrous giant son of the rain-goddess Callirhoe and a mortal son of Medusa named Chrysaor. Geryon is no taller than a man but has three complete bodies fused at the waist, all fully armored and helmed. He carries three weapons and three shields. Though monstrous, he was civilized, and content to live out his life herding cattle in a far land. Heracles was sent to capture Geryon’s cattle as one of his labors, and when Geryon attacked to prevent the theft, Heracles killed him. Despite his powerful ancestry, Geryon has little experience in combat and normally charges into battle with all of his weapons and loyal Orthos at his side.

An Intelligence (History) check reveals the following information: 10—Geryon was a triple-headed giant who guarded a great herd of cattle. 15—Heracles killed Geryon and his two-headed dog Orthos as part of one of his heroic labors.

Orthos

Medium beast, unaligned
Armor Class 14 (natural armor)
Hit Points 30 (4d8+12)
Speed 40 ft.

Saving Throws Dex +4, Con +5
Skills Perception +5, Stealth +4, Survival +3
Senses passive Perception 20
Languages Common
Challenge 3 (700 XP)

Ageless. Orthos cannot suffer from frailty of old age, die from old age, or be aged magically.
Snake-Tail. Orthos uses its Dexterity modifier for attack and damage rolls with its snake-tail.
Two Heads. Orthos has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

ACTIONS
Multiattack. Orthos makes two bite attacks and one snake-tail attack.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d6+4) piercing damage plus 4 (1d8) poison damage. If the target is a creature, it must succeed on a DC 14 Strength saving throw or be knocked prone.
Snake-Tail. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4+2) piercing damage plus 4 (1d8) poison damage.

Orthos is a two-headed snake-tailed dog, a smaller and weaker version of his brother Cerberus. Orthos served the monster Geryon and was killed by Heracles when Heracles tried to take Geryon’s cattle. According to some legends, he is the father of the sphinx and the Nemean lion (both mothered by the chimera). Like Cerberus, Orthos tries to trip an opponent and single out that creature for all his attacks.

An Intelligence (History) check reveals the following information: 9—The monster Geryon had a two headed-dog named Orthos, litter-mate of the beast Cerberus. 14—Like Cerberus, Orthos had a snake for a tail.