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

Hecatoncheire

Huge giant, neutral
Armor Class 15 (natural armor)
Hit Points 250 (20d12+120)
Speed 50 ft.

Saving Throws Cha +4
Skills Acrobatics +6, Intimidation +4, Investigation +7, Perception +9, Persuasion +4, Religion +7, Survival +9
Senses passive Perception 19
Languages Common
Challenge 12 (8,400 XP)

Ageless. The hecatoncheire cannot suffer from frailty of old age, die from old age, or be aged magically.
Improvised Rock. A hecatoncheire can throw any object and treat it as a rock. Items that are not bulky and heavy are treated as improvised weapons (1d4 damage, range 20/40 ft.) a hecatoncheire is proficient with.
Power Attack. When the hecatoncheire makes his first melee weapon attack in a turn, it can choose to take a -5 penalty to its melee weapon attack rolls in exchange for a +10 bonus to melee weapon damage. In addition, the hecatoncheire can use a bonus action to make one melee weapon attack after it uses a melee weapon to reduce a creature to 0 hit points or scores a critical hit with a melee weapon. A hecatoncheire can only use this feature on its turn.
Rock Catching. A hecatoncheire can catch Small, Medium, or Large rocks (or projectiles of similar shape) up to eight times per round, a hecatoncheire that would be hit by a ranged weapon attack can make a Dexterity saving throw against the attack roll. On a success, the hecantoncheire catches the projectile and can use its reaction to throw the projectile back at its attacker.

ACTIONS
Multiattack. The hecatoncheire makes any combination of 8 slam and rock attacks.
Slam. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 11 (1d8+7) bludgeoning damage.
Rock. Ranged Weapon Attack: +11 to hit, range 150/400, one target. Hit: 10 (1d6+7) bludgeoning damage.
Rain of Stone (Recharge 5-6). A hecatoncheire can hurl dozens of boulders in a devastating cascade of rocks that fills up a 400-foot long cone. Creatures in the area make a 19 Dexterity saving throw or take 55 (10d10) bludgeoning damage (half as much damage on a successful save). A creature 100 feet or further away from the hecaontcheire has advantage on their saving throw.

These three monstrous children of Gaea—Briareus, Gyes, and Kottos—each have one hundred arms and fifty heads. Cursing their ugliness, Uranos imprisoned the “hundred-handed ones” in Tartarus, but Zeus and the gods later freed them and with their help won the battle against the titans. The hecatoncheires may appear monstrous and brutish, but they are intelligent and noble like the best of the titans. Now they guard the gates of Tartarus, preventing the escape of the most evil titans who refused to make peace with Zeus and be freed.

An Intelligence (History) check reveals the following information: 8—The hecatoncheires (“hundred-handed ones”) are the younger brothers of the titans. Each is of huge size and has a hundred arms and fifty heads. 13—Uranos imprisoned them in Tartarus because they were so hideous, but Zeus and the gods freed them to help in the battle against the titans. 18—Loyal to the gods, the three brothers now guard the gates to Tartarus.