As a Fairy Rune Knight, what are my options for being strength based and still having a good armor class?

Question

The Fairy race, first printed in the adventure Supplement Wild Beyond the Witchlight, is a flying race that has the following restriction on the use of its flying speed:

Because of your wings, you have a flying speed equal to your walking speed. You can't use this flying speed if you're wearing medium or heavy armor.

This, combined with 5th edition's point buy setup, can make it rather challenging to make a Fairy character that uses Strength as its primary ability score. Since the fairy cannot wear medium or heavy armor and still benefit from flight, it is typically more suited to dexterity-based characters as well as spellcasters.

The Rune Knight Fighter from Tasha's Cauldron of Everything is interesting in many ways; one way is its Giant's Might feature. The two main effects of this are as follows:

If you are smaller than Large, you become Large, along with anything you are wearing. If you lack the room to become Large, your size doesn't change.

You have advantage on Strength checks and Strength saving throws.

This does several things for the Rune Knight. Most notably it makes them an exceptional grappler by granting them advantage on the relevant ability check, while also increasing their size to expand the size range of creatures they can grapple. Another minor thing it accomplishes is allowing a Small-sized Rune Knight to use Heavy weapons without disadvantage while the feature is active, and using such weapons is ideal for increasing damage output.

With Rune Knight being inclined towards Strength-based characters and Fairies being inclined towards Dexterity-based characters, how can I combine this race and class while minimizing complications? The options I can think of are as follows:

• Be dexterity-based, use Rapier and Shield, buy at least a 12 strength and take the Skill Expert feat to still be good at grappling
• Multiclass into Barbarian for Unarmored Defense as well as other advantages
• Buy a decent (14) dexterity and take the Defense fighting style

I am looking for options that would be available at the most levels of play possible, especially in tier 1, which makes multiclassing into Barbarian rather impractical, in addition to not yielding a spectacular armor class regardless. My preference for a character like this is to utilize two-handed weapons, but use non-heavy weapons when Giant's Might is not in use. For the most part, my desire to use Strength as the primary ability score mostly stems from the Rune Knight's grappling ability.

For the purposes of character building, I typically consider a 16 armor class to be "Ok", and an 18 armor class to be "Good" when it comes to the lower levels. Below a 16 armor class seems to be more realistic, so at least a 14 or 15 should be acceptable.

Answer 1

Magic Initiate + Mage Armor

If you can't wear regular armor, use magic armor.

A fighter receives a large number of ASIs, so use the one at level 4 to take the Magic Initiate feat, and choose sorcerer or wizard as your class and Mage Armor as your spell.

For 8 hours a day, you get 13 plus your DEX mod.

As one of your two free cantrips that you get with Magic Initiate, I suggest picking up Lightning Lure from Tasha's. It only requires a verbal component (so you don't need a free hand or focus) and doesn't require an attack roll. Instead, the target makes strength saving throw to avoid being pulled towards you.

If you are up against low strength targets, that synergizes well with your grappling strategy.

(I added this suggestion after realizing that spending an ASI to get Magic Initiate wasn't all that great when it could be spent on DEX instead to get the same AC benefit. It does still allow for a higher max AC if you get DEX all the way to 20 though.)

Point buy

Use point buy to get 14 and 15 in two stats, and then use the Faerie's racial ability score increase to make them both 16. Use these for STR and DEX. (I don't have access to the official rules for this, but what I've found on a summary page on D&D Beyond says this is available.)

Levels 1-3

Wear studded leather armor for 12 AC + DEX to reach 15 AC.

Levels 4+

Ditch all armor and use Mage Armor for 13 AC + DEX to reach 16 AC total, which is "Ok" by your standards.

Levels 6, 8, 12, and 14

Put your ASIs into STR and DEX to max them out at 20.

Result

This will get you a strength based fighter, with flying, plus the other benefits you want from Rune Knight, with 18 AC (20 with shield when not using two handed weapons) for 8 hours a day. And 17 AC for the rest of the day (by keeping that studded leather in your backpack.)

(Mix and match with other solutions to reduce how much DEX you need to get to make this work.)

Answer 2

With a DM that's willing to give specific magic items (or upgrade them) at certain levels or story beats, you could rely on Barrier Tattoos. They come in Uncommon, Rare, and Very Rare rarities, which roughly correspond to the highest AC choices of light, medium, and heavy armor. With 12 Dex you would have 13 AC with the first one, just like studded leather, but with the Rare version you would have 15 and Very Rare would give you 18. You would be able to use a shield as well as. You could work with your DM to flavor getting the rarer versions as adding to the tattoo you already have until you get to Very Rare.