Massive, dinosaur-like beasts, catamel stop for days at oases, collect water, and store it in large pouches on their backs. They consume this water as they spend weeks traveling in packs of 5 to 10 through the desert to the next oasis.
Desert predators sometimes target these water pouches, but they face a difficult climb up the catamel's sides, avoiding slaps from its tail and stomping legs.
For stats, I searched through all the gargantuan creatures and initially settled on the purple worm and the brontosaurus. However, the latter was too easy (and I wanted a creature with more attacks) while the latter felt too offensive for what's basically an elephant.
Baba Lysaga's Creeping Hut is actually closer in abilities, with its three attacks and siege monster ability. While I usually limit myself to monsters found in the Monster Manual, this is too close to ignore. So!
We'll skip the antimagic susceptibility, condition immunities, and damage immunities, and cut down on the range of its attacks. I'll offset those disadvantaqges with a resistance to bludgeoning, slashing, and piercing damage from non-magical weapons, plus higher Dexterity, Wisdom, and Charisma scores (since it's not, you know, a hut).
Okay, let's do this!
Homebrewery stat block:
Gargantuan beast, lawful
- Armor Class 16
- Hit Points 260 (17d20 + 82)
- Speed 30 ft.
STR DEX CON INT WIS CHA 26 (+8) 9 (-1) 20 (+5) 1 (-5) 7 (-2) 12 (+1)
- Saving Throws CON +9, WIS +2, CHA +3
- Damage Resistances bludgeoning, slashing, and piercing from non-magical weapons
- Senses Tremorsense 30 ft., Passive Perception 8
- Languages --
- Challenge 11 (7,200 XP)
Siege Monster. The creature deals double damage to objects and structures.
Multiattack. The creature makes three stomp attacks. It can replace one of these attacks with a tail whip attack. Stomp. Melee Weapon Attack: +12 to hit, reach 20 ft., one target. Hit: 30 (4d10 + 8) bludgeoning damage. Tail. Melee Weapon Attack: +12 to hit, range 60 ft., one target. Hit: 12 (3d8 + 8) bludgeoning damage.