If I submit my character sheet this will be mine:
He was the silent kid from the gang who loves playing MMORPG called Dragon Lair. Upon getting isekai'd he chooses to be one his favorite character, the Grand Master.

The Grand Master is a character that uses Weapon Change attacks to convert skills and maintain a consistent pace when attacking enemies.
Isekai name: Xian
Race: Human
Age: 20
Class: Grand Master (An advanced class of Knight)
Damage type: Magic
Character Debut/Theme
Errr…
You might want to look at the previous Character Sheets. Yours is missing a lot of information.
Also, we’re using Dungeons and Dragons 5e for determining classes and abilities. If you need help with that, don’t hesitate to ask. ^^”
<Snipped quote by Guardian Angel Haruki>
I'm currently presuming that the party would arrive in their base states with no abilities active, given they are basically just growing into fresh bodies. So, I wonder if Bartholomew would even be able to hide it from the party... It's funny though, but even if he can't hide it from them, when I really think about it, it's still incredibly hard to defend against without straight-up mind-reading. It's pretty clear to me examining that ability why changelings are often feared and hated, because it's absolutely sinister what they can do unchecked.
That’s a fair presumption. I do have a similar presumption with Ciel and her being a warlock: She wouldn’t have her warlock abilities until she actually makes a pact with the Djinni Patron.
Since it sounds like
@CaptainManbeard is considering taking on a pure GM role, that means contract terms may need to be hashed out in game. But I do imagine the prerequisite to make the contract being “
For the love of everything that is good, break up with Bartholomew!”
So, they might not even realize that Bart is a changeling until later or someone native to the new world points it out.
EDIT: Reread CaptainManbeard’s post! Sorry for the confusion on my end.