Protean Charm

From UnknowableWiki

The Protean Charm is a NEWT-level spell that makes given objects follow what happens to a master-object.

Hermione Granger casts a Protean Charm on all the fake Galleons she hands out to the Dumbledore's Army members, allowing them all to change according to the numbers Harry Potter sets on his own coin, and thus letting them know when the next meeting will be. The girl latter explains she got the idea from the Dark Marks engraved on the Death Eaters' arms (OP19).

Draco Malfoy, inspired by Hermione, uses the Protean Charm on two coins, allowing himself to send messages to an Imperioused Madam Rosmerta (HBP27).