By Alan McCoy from Dungeons & Dragons: Fundamentals
How to build challenging encounters against a Koalinth
Note: This has been prepared utilizing only the 5E Core Rules. The Koalinth can be found in “Ghosts of Saltmarsh” page 238-239, additional information pages 61-84. Also appearing in Polyhedron #89 and Dungeon #79.
The Koalinth are a primarily saltwater aquatic race of humanoids. Standing an impressive six-seven feet tall, they still fall within the range of medium sized creatures. Covered from head to toe in thick grey-green scales, some individuals have a chin frond that resembles a beard.
The Koalinth are an aggressive warrior race. Their culture is remarkably like that of the surface race: Hobgoblin. Koalinth are organized into bands of ten or so that are led by a Sargent, with ten bands gathered into a group called a century led by a Captain. Each member of a band has an assigned role inside the band, allowing for organized military action. Members of a Koalinth band are fiercely loyal to one another.
Koalinth are usually unknown to the surface races because they are continually engaged in a fierce and aggressive war for the domination of oceanic territory.
Step 1) Let us Review what we know about Koalinth
Physically, Koalinth are Strong (+1) and Tough (+1), though only slightly above average in Dexterity.
Mentally, Koalinth are average to slightly above average (no modifiers)Koalinth as remarked above, are an organized military society capable of and practiced in coordinated military tactics and strategy.
Koalinth are well protected against physical attack, their heavy scales as tough as scale mail.
Koalinth lack fins but do possess webbed hands and feet. Additionally, their Darksight is specifically useful in underwater environments allowing them to see normally in murky or muddied water.
While the Koalinth are strong swimmers, they are not fast swimmers, thus they tend to be slower underwater than many creatures. This tends to indicate that they were originally a surface race. Koalinth have been known to compensate for this by using underwater mounts and tow creatures.
Due to constant training and military drill, Koalinth are proficient in Athletics and Perception as well as Dexterity saving throws.Koalinth can speak Rudimentary Common and a unique dialect of Goblin.
Koalinth have Darkvision 60 feet and a passive perception of 12.Koalinth have fully functional gills as well as a limited lung capacity. They are not limited to underwater combat, though their time above the waves is limited.
Step 2) How do they Fight
The Koalinth are organized fighters beginning at the individual level. Every Koa has a partner, battle-mate, to which they are fiercely loyal. It is highly unusually to discover a Koa without their battle-mate.
First and foremost: while Koa might engage and occupy an enemy combatant, the group will swarm a single target attacking that individual until it is dead.
The choice of target will be by the Koa Sargent, and will usually focus on spellcasters first, melee combatants second.
Individually, the Koa fight with a trident (three to five tined spear), a dagger and a barb-thrower.
The barb-thrower is used as a missile weapon to harpoon and eventually allow capture of the target. A Koa, when fighting a creature engaged with its battle-mate (or any Koa) can utilize its martial advantage to deliver a powerful blow (+2d6 damage) once per round.
It is not unheard of for a group of Koa to have one of their members perform the HELP action and grant its compatriots Advantage on their attacks.
In groups, the Koa will also employ tactics such as nets to capture or otherwise incapacitate opponents. These nets are thrown, when a capture is made the Koa will depending on the orders of the leader either maintain direct control of the net or attach a weight that sends the net and its occupant into the deeps below.
Step 3) Role-Play Tips
The ruleset strongly suggests that the Koalinth are a form of aquatic hobgoblin. To a Koalinth, such a comparison would be insulting, suggestion that the Koalinth were somehow spawned from an inferior surface race would be grounds for immediate combat. They consider themselves to be superior to any of the myriad surface humanoids.
Below the waves, the Koalinth are engaged in a carefully planned military campaign designed to eventually propel them into full control of the deeps. Within this context, individuals who can aid in that struggle may be employed as allies. Additionally, the Koalinth have domesticated several underwater species to use as mount, guard, and attack animals.
Giant Crayfish and Sea Lions are mentioned, but other creatures are possible.In large scale battles, Koalinth Shamans and Witch Doctors will join the fray, as will a Standard Bearer. In the presence of their Standard, the morale and ferocity of all Koalinth will be increased. (Consider them to be under the effects of a BLESS spell).
Conversation with Koalinth can be achieved but will not be an easy process. The Koalinth can speak only stilted and fragmented Common, or their unique dialect of Goblin. They are of course, unwilling to allow a spell-caster to perform magic, considering all spells to be dangerous.
Step 4) Changes that should be made to the Official Stats entry
Koalinth ability scores are significantly below average, utilizing only 20 of the 27 points available to a player character. While I agree to a certain extent because encountered members of this race are typical, rather exceptional individuals, I still feel that they are entitled to 24 points (10% less) and racial modifiers.
I suggest: Strength 14, Dexterity 12, Constitution 14, Intelligence 10, Wisdom 10, Charisma 12. Racial modifiers increasing their Constitution as life below the waves is harsh, and their Charisma as their military training and discipline gives them both a strong sense of self and a significant amount of presence.
Weaponry: No sentient creature in its right mind throws away its primary weapon, thus the idea of the Koalinth using its trident as a missile weapon, while picturesque, is frankly, quite silly. Still, the Koa should have a missile weapon of some sort, therefore I suggest a barb-thrower (use light-crossbow statistics). This weapon also suggests the use of cables like those used in real world bow-fishing to harpoon and reel in prey or captives.
A Koalinth Trident should be considered polearm (reach 10 feet). When using a trident, Koalinth should be considered to have the Polearm Master Feat, enabling them to make opportunity attacks at 10-foot range and to make a bonus action melee attack with the reverse end when desired.If the above ability score change is adopted, the base AC of the Koalinth would be 15, if more protection is needed, the Koa can stir up the bottom silt, or toss forth a globe of squid ink etc. to obscure the battlefield and provide concealment. Note that their aquatic Darkvision would be mostly unaffected.