Mermaid

Mermaids are the premier aquatic species. They are tough, fast, and strong; they use their native terrain to great effect; and they cannot be engaged in battle in water by land-based units. Their problem, of course, is that they are fish out of water on anything but water tiles. Though the lack of water does not prohibit them from using most of their skills, Mermaids' combat capacity is still crippled by being on land.

Combat
Without an aquatic team, Mermaids are the terrors of the depths. They have unmatched agility in water and they are inherently tough with a large HP pool. They are extremely slow on dry land, however, and they are not that great of magicians.

Among all base species, Mermaids have the best health rating. Their health and Strength don't disappear on land and they remain decent fighters. But their performance in water tiles and water maps is another level - Mermaids' Aquatic trait turns them semi-Agile in water, allowing them to recover 2 APs per turn when no enemy in engagement is Aquatic themselves. Their Dive allows them to teleport to another water tile with a long range. Further they can create their own water with CreateWater. With how being Soaked weakens the offense and defense of other enemies, dealing with Mermaids that should be on similar power level in their native habitat will be a bitter lesson to learn.

Conversely, the terrain-based boosts Mermaids enjoy are, of course, not there without water. On land Mermaids have their speed severely limited, which exposes them to hit-and-run tactics or ranged attacks. CreateWater can flood tiles around them but mobility is still affected by the lack of large bodies of water. Water-related Skills and water spirits can alleviate some of these hindrances.

Aside their excellent interaction with water, Mermaids can use Regenerate - a 0 AP self-healing Skill. This further empowers their long-term durability. They can also learn WaterBolt. While Mermaids do not tend to have magically inclined genes, WaterBolt can still devastate lava-type enemies and debuff hard-hitting enemies and/or damage sponges, reducing their offense and defense at once.

Overworld
Mermaids' Aquatic movement type gives them excellent travel speed in water, but slows the party down on land unless a LandMount or AirMount of the proper size is in the party. Their CreateWater Skill can turn a plains tile into water tile or a lava tile into a stone tile from a range of 2, at the cost of 7 mana.

Breeding
Among all non-special aquatic species, Mermaids are the most fertile. Female Mermaids have arguably the highest reproductive potential among all base species once the fact that Aquatic eggs hatch twins is taken into account.

Mermaids generally don't have the magical genes to use their WaterBolt and Regenerate skills very effectively, but Mermaid hybrids with better magic such as Sirens or Water Angels can put them to good use if they inherit them.

Moneymaking
Mermaids' beauty is above average but not outstanding, and their only quirk with training sex skills is that they can't give footjobs (which doesn't really matter). They can fill open slots in the Brothel just fine but will be outshone there by other species.

They have no particular advantage toward collecting money or resources at home, but their Aquatic nature makes them suited to exploring ocean portals for crystals.

Trivia

 * Their vaginas are a lot more lubricated than normal, so the effect works even underwater. This makes it possible to insert even the biggest cocks with relative ease into their tight pussy.