Bankruptcy

This unassuming gold coin is actually a metal-devouring mimic, ready to eat through hoards of treasure. These are also parasites that 

It doesn't attack other creatures and has no strength to break most objects, but it'll flee when threatened. It has 1 hit point, 10 AC, a 35 ft. movement speed, a +6 bonus to Dexterity, and it makes any saving throws with a -3 penalty.

False Appearance. The mimic is indistinguishable from a gold coin while motionless, but its magical nature can be revealed by detect magic.

Financial Appetite. Bankruptcy is capable of eating through non-magical metal, stone and wood with relative ease, going through 1 inch of these materials in 1 hour, 7 min., and 6 seconds, respectively. It can also eat and digest most other materials, with the exception of crystals and glass.

The mimic has a special taste for coins, always preferring to eat some of them in place of anything else. Its rate of devouring is accelerated when it eats its favorite treats: it can eat up to 500 coins in 1 hour, regardless of the metal they're made of.

Blessing of the Sated. You can feed Bankruptcy coins to win its friendship. It becomes sated after being directly fed 10 gold coins, 120 silver coins, or 1500 copper coins, after which it sees you as their friend for 24 hours and needs to rest for 1 hour before eating again.

While it regards you as a friend, it will keep close to you, following you by your scent even if you're eventually separated. If left in the proximity of coins while you're friends, it'll come back to you after eating the whole of it or being removed from it.

Also, the mimic blesses you with fortune magic while you're friends. You have advantage on Dexterity (Sleight of Hand) checks during this period and you can choose to have advantage on one attack roll before the friendship ends.

Notes: Advantage: Sleight of Hand