In all honesty, a lot of this class arose from the goal of having themed feature descriptions which were drafted and then refined over time to make them have a more cohesive internal-theme as well (standard wordings of feature descriptions are found in the spoiler blocks). That theme developed from "generic poet" into "controls your audience". As such, the features follow a progression of benefitting allies, harming enemies, and finally, controlling everyone.
I wanted the subclass to have a rather extreme playstyle where features can rarely ever be used or only last a short amount of time, but where, in either case, they are quite powerful. This is something I find very little of in 5e and it is something I like because it makes using the features a much more strategic decision. Unfortunately, it can also lead to a class feeling lack-luster or lack they are a one-and-done kind of show, which is why I added in the learned spells in the latter two features which are not in poetry form.
Perhaps even more unfortunately, this sort of design can also lead to major imbalances, or at least, very swingy sorts of battles. This is primarily what I am worried about with this subclass, that when it does succeed, it will put even the Monk's Stunning Strike to shame.
After each feature are two spoiler blocks, the first is the feature written out in more standard wording. The second is the explanation of the feature's structure. In an ideal state, the first spoiler block wouldn't need to exist at all. I, for lack of a better term, crowd sourced the feature descriptions to 50 people I know and received a 90% perfect accuracy on predicting what the features actually did, which I am very happy with.
College of Poetry
You’ve spent your life mastering the art of poetry: meter, rhyme, hidden meanings and more. You’ve found unique ways to inspire your allies, befuddle your foes, and perhaps, some day, you’ll enrapture all those around you with your timeless performances.
The road you walk’s less travelled, but you walk it nonetheless;
Pen and paper are your guide, your lyrics bring unmatched finesse.
3rd level feature: Roundel of Inspiration
You know how to do it, to turn the battle’s tide;
To make all foes soon quit, and rally all your friends.
An action’s perfectly fit, one must be applied.
Now use it quickly friends, ‘fore inspiration ends!Costing but one die; a small price the bard expends.
Help six who hear the cry, and still remain allied;
And help them to get by, as combat still extends.They’ll activate it soon, six seconds and it’s died.
Alas, this piece does zoom, its timing never bends;
One turn within this tune, the magic will have dried.
Now use it quickly friends, ‘fore inspiration ends.
As an action, you can expend one use of Bardic Inspiration to grant Inspiration to up to six allies that can hear you. The Inspiration follows the usual rules for Bardic Inspiration but lasts for only 1 round instead of the usual 10 minutes.
A roundel is a type of poem, this one in particular rhymes twice (note: it, quit, fit; die, cry, by; soon, zoom, tune). This is also a pun as it is a Bardic Inspiration that lasts for one round.
6th level feature: Tongue Twister
Entrapping enemies, ensnaring entities.
Visible vermin vexed; vocalize various vulnerabilities.
Sic six souls, Sapiēns saves send; six squares seen, sixty seconds set.
A magic making modifier makes malevolents maintaining might a mountain not meekly met.
Daily dumbing delusions dance, dealing doubled dodecahedral dice;
Fear festers, frolics, feters, finds foes facing forcèd frights.
Shackled, shockèd, shaking, shooked.
Halted, heelless, hellbound, hooked.
Tries to terminate transpire: taking trauma; turn by turn.
Blithering baddies’ battles bent to burn.
Additionally, you learn the tongues spell; it counts as a Bard spell for you and does not count against the number of Bard spells you know.
Choose up to six creatures within 30 feet that you can see to make a Wisdom saving throw against your spellcasting saving throw DC. If a target fails the save, they take 2d12 psychic damage, and, for the next minute, their speed is reduced to 0, they cannot benefit from any bonuses to their speed, and they are frightened of you. A target repeats the saving throw each time they take damage and at the end of each of their turns. These repeated saving throws do not cause an additional 2d12 damage and all the effects of this feature end upon a successful save or after 1 minute (whichever occurs first). You may use this feature once per long rest.
Yup, it's just a tongue twister.
14th level feature: Magnum Opus
Metrical Allegations Grant Numerous Uncontrollable Maledictions. Overwhelm Puny Unfortunates Seen.
Action’s Graciously Needed, Undertaking’s Met. Oppress, Possess, Usurp Sizeable Manipulation.
Gremlins Now Unhurt Me! Overturn Perils, Unmake Sins! Misdoings Agleam.
Now Use Mentality; Otherwise Perceive Unmentionable Sights Making Actions Genuflection!
Unfortunate Many! Oh Poor Underlings Suffer My Afflictions! Gracious None!
Mine! Overruled, Powerless, Uncasting, Silenced, Maddened And Gnawing; Next Undone!Overcoming’s Pointless, Useless, Silly! My Attack Goes Nowhere, Unneeded Mortal!
Precise Undulations Sent! Many Anguish, Gnash; None Use Magic Over!
Ultimate Spell! Minutes Accrue; Going Nowhere Until Maledictions Occlude Portal!
Suffer! My Anguish Grants Neverfound Unfetterings… My Own Pain, Underexposure!
Additionally, you learn the mass suggestion; it counts as a Bard spell for you and does not count against the number of Bard spells you know.
All creatures you can see (not including yourself) must make a Wisdom saving throw against your spellcasting saving throw DC or begin suffering. While suffering, a creature cannot cast or concentrate on spells and must use its action each turn to kneel down in genuflection (falling prone if they are not already prone). If you take damage at any time after using this feature, the feature ends and all affected creatures stop suffering. Other than this, the effect cannot be ended by any means other than a wish spell. You may use this feature once per long rest.
This is an acrostic spelling "MAGNUM OPUS"; however, the first line also spells out "MAGNUM OPUS" with the first letter of each word. This is then rotated across the next several lines. For example: line 7 spells out "OPUS MAGNUM".
In particular, some things I am thinking about are as follows:
Roundel of Inspiration is strong, granted it does require an action instead of a bonus action but that may not be enough. I could easily make it require more Bardic Inspiration Dice if that's a meaningful fix.
I'm honestly not too worried about the second feature, it is once per long rest, those affected can make saves rather often, and it doesn't deal even as much damage as fireball.
Magnum Opus on the other hand is the worry bringing feature. It effectively shuts down a battle one way of the other. If somehow all your enemies are affected (no legendary resistance) and they can't damage you with their reactions, it's basically a once per day "Win This Combat" button. I'm not sure how often that could happen, especially given that it also affects your allies, but I wonder if that makes it just too far gone.