Fomorians are yet another manifestation of the “evil ≡ ugly” essentialist trope, which I wish would go away. Once a noble and beautiful strain of giantkind, they were cursed with a warped and hideous appearance for their hubristic crimes against the Feywild. Not only was their pulchritude taken from them, they lost their intellectual brilliance as well: the average fomorian has an Intelligence of only 9.
Extremely strong and tough brutes, with a hefty reservoir of hit points, fomorians barrel directly into the fray. Their Evil Eye feature works out to a range of 60 feet, but they use it from the midst of melee. Long-range darkvision suggests that they dwell in darkness—either underground, where they’re most commonly found, or in the densest and gloomiest of forests—and don’t attack when there’s a bright light source present.
Their low Intelligence and high Wisdom are an interesting juxtaposition. By my reckoning, Intelligence represents logical assessment, while Wisdom represents judgment as well as perception. Fomorians’ situational awareness is a mixed bag: They’re pretty good at assessing whether or not a fight is winnable, and they refrain from engaging when it’s not, but they lack tactical breadth and target selection savvy. Once they’ve committed to a fight, their behavior is relatively simple, and their decisions arbitrary.
Thanks to their expertise in Perception and proficiency in Stealth, they’re capable ambush attackers, and they may trail a group of characters for a while before deciding whether or not to attack. Once they choose to do so, they try to make that first attack while still unseen, to gain both advantage and surprise. Based on their lore, I’d say they strike first at elves and other races with Fey Ancestry if possible, just out of spite. But there’s nothing in their stat block that compels them to, so feel free to disregard that if you wish.
Once they’ve engaged in melee, they strike at whoever’s nearby and striking at them. Their greatclub deals an average of 19.5 points of damage per hit; their Evil Eye deals 27 on a failed save and 13.5 on a success, for expected damage of 20.25, give or take. This seems like a pretty insignificant difference until you consider that a melee hit isn’t assured: the expected damage of a melee attack is less than the average damage on a hit, owing to hit probability. Even with +9 to hit, a fomorian still has only, say, a 60 percent chance of damaging an enemy wearing chain mail and carrying a shield, reducing its expected melee damage to 11.7. Evil Eye is definitely stronger.
However, based on their low Intelligence, I’m going to suggest that fomorians have tunnel vision: having chosen a target to whomp, they keep whomping that target unless and until they take damage from another source. Only then do they start using the Multiattack option of splitting their attacks between their greatclubs and their Evil Eye. Moreover, because of their brutish melee bias, they use Evil Eye only against targets who are out of reach of their clubs (i.e., more than 15 feet away). If they’re taking both melee and either ranged or area-effect damage, they always use Evil Eye against an attacker who dealt one of the latter.
Curse of the Evil Eye is a one-use-per-combat feature, and it also consumes a full action, which might otherwise be used to Multiattack. Thus, despite being the fomorian’s most powerful attack, it’s also one that it has to use judiciously—and fomorians aren’t mentally equipped for judiciousness in the midst of battle. We need a simple criterion that will trigger the use of the fomorian “nuclear option.”
How about this: If and when an opponent manages to singlehandedly do moderate damage—at least 45 points—to a fomorian, that’s when it gets enraged enough to use Curse of the Evil Eye, and it uses it against that opponent. If this curse doesn’t succeed, the fomorian is prudent enough to realize that the tide of battle is turning against it, and it begins to retreat, continuing to attack while moving away from its foes.
If the fomorian is never driven to use Curse of the Evil Eye but is seriously injured (reduced to 59 hp or fewer), it also recognizes that it’s time to leave; in this instance, however, it simply Dashes away rather than continue to swing its club as it retreats. If it’s pursued by only a single enemy, it may slow down to use the Evil Eye against that enemy as it continues to move away.
A final thought: I have no idea where the DC of the fomorian’s Evil Eye comes from. It doesn’t seem to be tied to any of the fomorian’s ability scores. Based on the difference between the fomorian’s attack modifier and its damage modifier, we can deduce that it has a proficiency modifier of +3, but this would suggest that its Evil Eye should be based on an ability with a +3 modifier—which it doesn’t have. Is the Evil Eye Wisdom-based? Then the DC ought to be 13. Constitution-based? Then it ought to be 16. Based on the fomorian’s challenge rating (“Creating Quick Monster Stats,” Dungeon Master’s Guide, page 274)? Also 16. I’d love to know the developers’ rationale for setting the DC at 14.
Next: elder elementals.