Cachalot (5e Creature)
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Gargantuan beast, unaligned
Charge. If the whale moves at least 20 feet straight toward a creature and then hits it with a slam attack on the same turn, the target takes an extra 13 (2d12) bludgeoning damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be knocked prone. If the target is prone, the whale can make bite attack against it as a bonus action.
Hold Breath. The whale can hold its breath for 90 minutes.
Siege Monster. The whale deals double damage to objects and structures.
Multiattack. The whale makes two attacks: one with its bite and one with its tail. It can't make both attacks against the same target.
Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 23 (3d10 + 7) piercing damage. If the target is a medium or smaller creature it is grappled (escape DC 20). Until this grapple ends, the whale can't bite another target.
Slam. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 39 (5d12 + 7) bludgeoning damage.
The cachalot is a giant cetacean seen very rarely, for they often dive to deep depths. They're also known as sperm whales after their spermaceti, a waxy substance in the whale's head cavity, which is considered valuable. It is for this that they're hunted, however, they've been known to sink even the largest of whaling ships, often with a well-placed ram.