College of the Moon Bard

 Tied lorewise to the Moonshae Isles (though of course, you can always reflavor things as you see fit,) the Moon Bard evokes druidic and fey magic - the latter of which feels like a really solid fit for the Bard class as a whole.

Level 3:

Moon's Inspiration:

You gain two benefits: Inspired Eclipse gives you a secondary effect when you grant Bardic Inspiration with a bonus action: you can now become invisible and teleport up to 30 feet to an unoccupied space you can see. The invisibility ends at the start of your next turn, or if you make an attack roll, cast a spell, or deal damage in any other way.

    Bards can be somewhat squishy, and this turns your BI into a Misty Step with extra benefits, so this is pretty nice.

Lunar Vitality, the other effect, lets you expend a BI die when you restore hit points to a creature with a spell to increase the HP restored by a roll of the BI die. The creature's speed also increases by 10 feet until the end of their next turn.

    I'm skeptical you'll often want to expend this resource for just a little extra healing, though the speed boost combined with that could give a downed character the extra oomph to spend their turn getting out of danger.

Primal Lore:

You learn Druidic and one cantrip from the Druid spell list. It counts as a Bard spell for you but not against the number of cantrips you can learn. You can replace this cantrip when you gain a Bard level with another Druid cantrip. Additionally, you gain your choice of proficiency in Animal Handling, Insight, Medicine, Nature, Perception, or Survival.

    Druid cantrip to me often screams "Shillelagh," as it's a way to let spellcasters use their best stat for a weapon. But there are other options here.

Level 6:

Blessing of Moonlight:

You always have Moonbeam prepared. When you cast it, you can modify the spell so that you also faintly glow, shedding dim light out to 5 feet, and whenever a creature fails a save against this Moonbeam, another creature within 60 feet of you regains 2d4 HP. You can cast the spell this way once per long rest.

    Moonbeam's radius is small, but you can potentially catch multiple foes within it, and I think that this healing will work even if multiple foes fail the save at the same time. It's not a ton of healing, but it's something. Also, the fact that you glow feels more for flavor than anything else.

Level 14:

Eventide's Splendor:

You gain two benefits:

Shadow of the New Moon causes your Inspired Eclipse to also grant the recipient of your BI invisibility (if they want it) and allows them to use a reaction to teleport up to 30 feet to an unoccupied space they can see. They remain invisible until the start of their next turn (meaning that they might stay invisible through an opportunity attack or reaction spell).

    Certainly pretty good to give you some ways to help your allies teleport around.

Vibrance of the New Moon lets you, when you use Lunar Vitality, roll 1d6 instead of the BI die and add it to the healing without expending a BI die.

    So you're always healing 1d6 more. At this level, that's not a ton.

Overall Thoughts:

So, I think this will allow some fun flavor: there's definitely a "tricksy fey" vibe to this subclass. And I always have to remind myself that Bard subclasses always feel thin because there are only three levels at which you get features.

I'm not sure that this is really inspiring me, so to speak. There's a little taste of something flavorful here, but while the visuals of a Moon Bard seem very cool, I don't really see a lot of potential or power in its mechanics.