Hill Giant Death's-Head
Medium undead, chaotic evil
Armor Class 13 (natural armor)
Hit Points 85 (10d8 + 40)
Speed 5 ft
Str 21 (+5) Dex 8 (-1) Con 19 (+4) Int 5 (-3) Wis 9 (-1) Cha 6 (-2)
Skills Perception +2
Condition Immunities poisoned, prone
Senses passive Perception 12
Languages Common, Giant
Challenge 2 (450 XP)
Giant-kind: A death's-head is made from the head of a freshly-slain giant. It also has the Giant type.
Actions
Multiattack. The hill giant death's-head makes two bite attacks.
Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 14 (2d8+5) piercing damage.
Shout (Recharge 5-6). The hill giant death's-head lets out a great shout that can be heard up to 500 feet away. All creatures in a 20-foot cone must roll DC 14 Constitution saving throws, suffering 3d8 thunder damage on a failed save, or half that on a success. The hill giant death's-head can choose to be pushed in the opposite direction of the cone, any distance up to 20 feet. Creatures in the path of its movement must roll DC 14 Strength saving throws, falling prone on a failure.
Stone Giant Death's-Head
Medium undead, chaotic evil
Armor Class 17 (natural armor)
Hit Points 105 (11d8 + 55)
Speed 5 ft
Str 23 (+6) Dex 15 (+2) Con 20 (+5) Int 10 (+0) Wis 12 (+1) Cha 9 (-1)
Saving throws Con +7, Wis +3
Skills Perception +3
Condition Immunities poisoned, prone
Senses passive Perception 13
Languages Common, Giant
Challenge 4 (450 XP)
Giant-kind: A death's-head is made from the head of a freshly-slain giant. It also has the Giant type.
Stone Camouflage. The stone giant death's-head has advantage on Dexterity (Stealth) checks made to hide in rocky terrain. It is easily mistaken for a boulder or a rock carving.
Actions
Multiattack. The stone giant death's-head makes two bite attacks.
Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8+5) piercing damage, and it may choose to initiate a grapple, rolling Strength (Athletics) +6 against the target's Strength (Athletics) or Dexterity (Acrobatics).
Grind. The stone giant death's-head grinds its teeth on a creature it has grappled. The creature rolls a Strength saving throw against DC 16, suffering 33 (5d10 + 6) bludgeoning damage on a failure, or half damage on a success.
Frost Giant Death's-Head
Medium undead, chaotic evil
Armor Class 13 (natural armor)
Hit Points 114 (12d8 + 60)
Speed 5 ft
Str 23 (+6) Dex 9 (-1) Con 21 (+5) Int 9 (-1) Wis 10 (+0) Cha 12 (+1)
Saving throws Con +8, Wis +3, Cha +4
Skills Perception +3
Damage Immunities cold
Condition Immunities poisoned, prone
Senses passive Perception 13
Languages Common, Giant
Challenge 5 (1,800 XP)
Giant-kind: A death's-head is made from the head of a freshly-slain giant. It also has the Giant type.
Actions
Multiattack. The frost giant death's-head makes two bite attacks, or one treacherous winds attack and one bite attack.
Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 14 (2d8+5) piercing damage.
Treacherous Winds. The frost giant death's-head opens its mouth and inhales mightily, drawing nearby creatures closer. Creatures within a 30-foot cone must roll a Strength saving throw against DC 16 or be pulled 15 feet closer to the death's-head. Until the death's-head uses any action other than treacherous winds, the creature cannot move away from the death's-head except through teleportation. At the end of the target's turn, it may make a saving throw, ending the effect on a success.
Fire Giant Death's-Head
Medium undead, chaotic evil
Armor Class 13 (natural armor)
Hit Points 136 (13d8 + 78)
Speed 5 ft
Str 25 (+7) Dex 9 (-1) Con 23 (+6) Int 10 (+0) Wis 14 (+2) Cha 13 (+1)
Saving throws Con +9, Cha +4
Skills Perception +6
Damage Immunities fire
Condition Immunities poisoned, prone
Senses passive Perception 16
Languages Common, Giant
Challenge 6 (2,300 XP)
Giant-kind: A death's-head is made from the head of a freshly-slain giant. It also has the Giant type.
Actions
Multiattack. The fire giant death's-head makes two bite attacks.
Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 14 (2d8+5) piercing damage and 4 (1d8) fire damage.
Aura of Burning Earth. The fire giant death's-head channels fire into the earth in a deadly aura. While it is in contact with solid ground, all creatures that begin their turns within 10 feet of the fire giant death's-head, or enter that area during their turns, take 2d6 fire damage, or half damage if they are not in contact with the ground. This effect ends if the death's-head ends a turn more than 10 feet from where it started its turn, or out of contact with the ground.
Design Notes
Giant death's-heads have obvious and serious limitations in terms of mobility, which they make up for with dirty tricks and being very good at raising an alarm. Still, they're at their most effective in tight quarters, where their enemies have limited maneuverability too.
Working on this really drove home for me the fact that hill, stone, fire, and frost giants are pretty much sacks of hit points that kick out pretty good damage. They have good flavor text, but their mechanics are shockingly plain even by 5e standards. They do have a lot of proficient saving throws, by monster standards, but still. (I understand that this is addressed in Volo's Guide to Monsters, and possibly also Storm King's Thunder, but I don't have either of those just yet.) It's an interesting point of comparison back to 3.5e, where the monster-creation rules obliged designers to give them a substantial list of feats that, in turn, gave them more involved combat actions.
Use these fairly sparingly, emphasizing the what-the-fuck-is-that factor and the overall freakiness of being attacked by a giant head.