D&D 5E Motto for Thieves' Guild

[aramis erak]

Anything I can pry up wasn't nailed down, and anything not nailed down is mine!

 

[Rydac]

If they're welcoming the character into the guild why not the classic
"Hail Hydra"

 

[steeldragons]

Surely you mean "Hail Cobra!"

 

[PnPgamer]

The Nighthawks could use Caprimulgus [Wikipedia entry: A nighthawk is a nocturnal bird of the subfamily Chordeilinae, within the nightjar family, Caprimulgidae. Nightjars are sometimes referred to as goatsuckers from the mistaken belief that they suck milk from goats (the Latin for goatsucker is Caprimulgus).]

So nighthawks motto is "Got milk?"

 

[Athinar]

I work for the Federal Government or I work for the IRS

 

[Unwise]

My suggestion is Carpe Omnia over a crest of a fish and a bird.

Carpe omnia = grab it all
Fish = refered to as "Poisson" in heraldry.
Bird = a dart

So a motto that amounts to take it all with a poison dart as the heraldic symbol.

 

[Dannyalcatraz]

A motto usable as split statement:

"To the 7 Bells, unrung."

Refers to the Suit of Seven Bells, which (some traditions of) pickpockets use to learn & hone some of their skills. It is a suit with a bell sewn over location of a pocket or purse. The object is to remove something from (or sometimes, place something in) a pocket without ringing the bell.

 

[Mick Miller]

Vae victis. Latin for Woe to the defeated (or victims).

 

[Charlaquin]

Snitches get stitches

 

[Draegn]

Never leave home without your running shoes on.