Amphicoelias (5e Creature)
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Gargantuan beast (sauropod), unaligned
Saving Throws Str +19, Con +19, Wis +16
Legendary Resistance (3/Day). If the amphicoelias fails a saving throw, it can choose to succeed instead.
Living ecosystem. The amphicoelias's is immune to any spell or effect that would alter its form and Beasts and Plants have disadvantage on attack rolls against it.
Thick Skin. If an attack deals less than 50 damage to the amphicoelias, the damage is reduced to 5 (before resistances).
Multiattack. The amphicoelias makes two attacks: one with its stomp and one with its tail.
Stomp. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 175 (30d10 + 10) bludgeoning damage. If target is a creature, it must succeed on a DC 24 Strength saving throw or be knocked prone. If the creature is already prone any hit with this attack counts as a critical hit.
Tail. Melee Weapon Attack: +19 to hit, reach 40 ft., one target. Hit: 98 (16d10 + 10) bludgeoning damage, and each creature within 30 feet of the ampicoelias must succeed on a DC 25 Constitution saving throw or take 32 (6d10) thunder damage and be deafened for 1 minute. An affected creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
The amphicoelias is a sauropod shrouded in legend. There are said to be a herd somewhere in the dense Chuult rainforest. These creatures are the largest land animal people may see. The largest adult killed was 155 feet long, some say they have seen larger. These creatures act like mobile ecosystems and some argue they are sapient. The life force they emanate grants them incredible longevity and makes them resistant to disease, the lush moss that coats their skin protects them from flames, and their thick skin makes them immune to most forms of harm.