Tasha Preview, Wild Magic Barbarian and Genie Warlock

[Edea]

I must be blind. What "proficiency for low-level features" are people talking about?

Spoiler: Bottled Respite (1st Level)

Show

You can remain inside the
vessel up to a number of hours equal to twice your
proficiency bonus.

Spoiler: Genie's Wrath (1st Level)

Show

Once during each of your turns
when you hit with an attack roll, you can deal extra
damage to the target equal to your proficiency
bonus.

Spoiler: Elemental Gift (6th Level)

Show

In addition, as a bonus action, you can give yourself
a flying speed of 30 feet that lasts for 10 minutes,
during which you can hover. You can use this bonus
action a number of times equal to your proficiency
bonus, and you regain all expended uses when you
finish a long rest.

Sanctuary Vessel runs off Bottled Respite, so technically that one, too.