How to break the sound barrier without a heavily restricted character?

Question

I've seen a number of TikTok and YouTube videos recently about breaking the sound barrier in D&D. The builds proposed by these videos are very restrictive, so I was wondering if this feat could be done with less restricted builds.

For the purpose of this question, "breaking the sound barrier" means physically moving (i.e. not teleporting) at least 6,900 feet with your movement within one round. This only needs to be achievable reliably (100% of attempts) at least once per day, and you can use any non-legendary magic items, multiclassing, and feats. You may not use magic items that permanently boost Ability Scores, Epic Boons, or assistance from other characters that you cannot summon yourself.

What 20th level character build can break the sound barrier with the most liberty remaining in their build? I consider the following selections to be key to a character build, and thus would rather their liberty be preserved. The less of these that are required for the speed feat, the better the answer.

• Character race
• Character primary class (the class with the most levels)
• Character primary subclass (for the class with the most levels)
• Number of levels needed for multiclass dips
• ASI/feat selections
• Attunement slots

For the purposes of the question, I will treat all of these as equally important to build liberty, so my evaluation of build liberty uses the following formula:

• 1 point if character race is free
• 1 point if the majority of class levels (at least 11) are free
• 1 point if the primary class does not have a required subclass (guaranteed if the primary class if free)
• 1 point for each level that is not restricted (assuming the primary class goes to level 11)
• 1 point for each ASI/feat selection that is free (not counting extra ones from Rogue or Fighter)
• 1 point for each attunement slot that is free

Answer 1

7 points of build liberty

The Character

Our sonic boomer, let's call him Crash, is a 20th level Tabaxi with the following classes:

• Bard 10 ------------------------------------- (for longstrider, Jack of All Trades, the Metamagic Adept feat, the Mobile feat, and Ashardalon's stride via Magical Secrets)
• Druid (Circle of the Stars) 2 -------------- (for the spell list and Starry Form: Dragon)
• Fighter 2 ------------------------------------ (for Action Surge)
• Monk 2 -------------------------------------- (for Unarmored Movement and Step of the Wind)

...and the following magic items:

• potion of speed
• spell scroll of wind walk

The Charge

To break the sound barrier, Crash follows this procedure:

• Use Starry Form choosing the Dragon constellation
• Cast longstrider
• Drink the potion of speed
• Cast Ashardalon's stride with the Extended Spell Metamagic
• Use the spell scroll of wind walk (guaranteed due to Starry Form: Dragon, 16 Wisdom, and Jack of All Trades)
• Use Feline Agility
• Take the Dash action
• Take the Dash action using Step of the Wind
• Take the Dash action using the action granted by the potion of speed
• Take the Dash action using the action granted by Action Surge

The Calculation

To start with, here is Crash's base movement speed:

• 300 feet (wind walk) [total so far]
• 10 feet (Unarmored Movement) [310 feet]
• 10 feet (Mobile feat) [320 feet]
• 10 feet (longstrider) [330 feet]
• 20 feet (Ashardalon's stride) [350 feet]

This is then doubled by:

• potion of speed [700 feet]
• Feline Agility [1400 feet]

Crash can use this speed 5 times due to 4 dashes resulting in 7000 feet

For the build, he gets:

• 1 point of build liberty since any bard subclass is sufficient
• 3 points of build liberty since 3 levels are flexible after Bard 11
• 3 points of build liberty for free attunement slots