Sahuagin are fierce, amphibious fish-men that live underwater but emerge periodically to raid coastal settlements. Although the Monster Manual says they “dwell within the deepest trenches of the ocean,” that’s a touch far for even a creature with 40-foot swimming speed. Those ocean trenches are as far away from the coasts because the highest mountains are, and you don’t often hear about the yeti of the Himalayas spending a day staging a raid on Kolkata, or the Tatzelwürmer of Alps popping right down to Genoa for a few late-night ravaging. These are distances of many miles we’re talking about. So the likelihood is that any sahuagin that player characters encounter are getting to be denizens of shallower depths. Maybe they’re the border reivers of the ocean kingdom.
When they come ashore to raid, they are doing so in the dark, as implied by their 120 feet of dark vision. They can’t come far inland since their Limited Amphibiousness gives them only four hours of air-breathing before they need to return to the water. Unlike, say, merrows, sahuagin can move about ashore as easily as the other humanoid.
Armor Class 12 (Natural Armor)
Hit Points 22 (4d8+4)
Speed 30 ft., swim 40 ft.
STR DEX CON INT WIS CHA
13 (+1) 11 (+0) 12 (+1) 12 (+1) 13 (+1) 9 (-1)
Skills Perception +5
Senses Darkvision 120 Ft., passive Perception 15
Challenge 1/2 (100 XP)
In this environment, they’re basic brutes. Their Multiattack gives them one weapon or claw attack and one bite attack. Since their armor class doesn’t include a shield, we will presume that they wield their spears two-handed for the greater damage.
Sahuagin within the water is additionally more tenacious than sahuagin ashore. When fighting underwater, they’ll persevere there until a majority of them are seriously wounded (reduced to eight hp or fewer). then, they’ll Disengage and retreat if they’re on their own, but they’ll fight to the death at the command of a sahuagin baron or priestess—usually so as to defend a location or object.
The presence of a priestess also keeps a moderately wounded group of sahuagin within the fight longer: anytime all the sahuagin within the group are reduced to fifteen hp or fewer, the priestess casts mass healing word to top them a copy, then uses either the assistance action or the Dodge action, as in round 1, until all its 3rd-level spell slots are gone.
Finally, in any group of sahuagin with both a baron and a priestess, it’s the priestess, not the baron, that’s the de facto leader (whether or not the baron cares to admit it). If a PC tries to start out a parley, the priestess will call a halt to combat and cast tongues to permit the 2 groups to speak. It’s unlikely that the sahuagin will ever initiate a parley on their own, however, unless they know they’re outmatched and aren’t guarding anything super-important—and unless they need a priestess with them because they know most land creatures don’t speak their language.
Sahuagin priestesses call a general retreat when they’re moderately wounded (reduced to 23 hp or fewer) unless they’re guarding a crucial location or object, during which case they defend until they’re seriously wounded (reduced to 13 hp or fewer). Sahuagin barons will always fight until they’re seriously wounded (reduced to 30 hp or fewer), then call a general retreat.