Doom Cobra (5e Creature)
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Huge beast, unaligned
Hold Breath. The cobra can hold its breath for 15 minutes.
Bite. Melee Weapon Attack: +6 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage, and the target must make a DC 14 Constitution saving throw, taking 21 (6d6) poison damage on a failed save, or half as much damage on a successful one.
Doom cobras, so named for their ferocious bite which carries an incredibly potent toxin that all but spells death for those bitten, are large snakes with incredible green and brown scaly hides, which function like chain links to soften the impact of the attacks of struggling prey. They rarely attack humanoids unless provoked, but attacks are almost always fatal, either from the powerful bite, or the diabolical venom that follows.