So that's.
STR | DEX | CON | INT | WIS | CHA |
---|
20? (+5) | 7? (–2) | 17? (+3) | 9-10 (+0 or –1) | 9? (–1) | 5? (–3) |
Okay, going through them in order.
Strength 20. Hmm, my gut tells me STR 18 or 19 (+4) would be better. That'd give it a +6 to hit, one less than the +7 of a 5E Troll, since in AD&D a normal Troll has THAC0 13, a step better than the THAC0 15 the Cyclops would have in those rules.
Also, it'll have
Multiattack with one bite and one or two claws, and each of those attacks will get its Strength bonus on the damage. Three sets of +5 will makes its Damage-Per-Round three points higher than three sets of +4.
Dexterity 7. Seems too low. They don't
need to be as clumsy like an ogre, they might be as agile as a troll (DEX 13 in 5E). The one eye probably makes it hard for them to hit thinks, but its eyesight is probably at least as keen as a human's (it's a LOT bigger than a human eyeball, so may be keener), and it could have as good a range of field depending on its optics. It's the depth perception that's poor, at least that's the only penalty mentioned in the original text.
Plus, wouldn't a Fey tend to be more agile than a clumsy ogre, not less?
I'd go for something in the (–1) to (+2) range, so anywhere from an Ogre's 8 to a Bugbear or Stone Giant's 14. Would prefer 12-13 (+1) to help distinguish it from a bog standard giant.
Constitution 17. I'm OK with that and 8 HD or 9 HD, or CON 15 and 9 HD or 10 HD. My favourite at the moment is CON 17 and 9 Hit Dice, but I'm not that attached to the idea.
Let's go for your suggested CON 17 and 8 Hit Dice for now, but we might need to tweak it later to achieve a particular Challenge Rating. We won't know until we sort out the Actions.
Intelligence 9 or 10. Either is fine, but we have to pick one!
Wisdom 9. Works for me.
While its ability so see through Illusions might suggest it's highly perceptive, that's more likely to be a special trait. If it
is good at noticing things due to its oversized eye, that can be achieved with skill proficiency in Perception (or even double proficiency), although keen eyesight like a Giant Eagle or Blood Hawk might be more appropriate. Or give them both
Skill in Perception and
Keen Sight?
Charisma 5. I'd argue that's too low for two reasons:
First, they frequently control groups of humanoids (goblins, orcs, et cetera) which would be trickier if they have pathetic Charisma.
Secondly, their Hypnotic Gaze would have a Charisma-based saving throw if we use the default ability for gaze attacks. The next most likely ability is Wisdom, which I'd be OK with but that'd just mean I'd want to increase its WIS score instead.
Just cause it's a horrible monster doesn't mean it has to have a low Charisma. If it's good at terrifying creatures into doing its bidding that implies it has a high Charisma, it's just a nasty one!