Ledger of true names (Eldritch Invocation)

Whenever a creature tells you a name it identifies as, you can write it into your Book of Shadows. You can cast any spell on to creatures with their name(s) in your book as if they were in range. The spells target  has disadvantage for its first save against your spell, when the spell involves an attack, you have advantage on it. You can use this feature a number of times equal to 1 + your Charisma modifier (min. 2). You regain all uses after finishing a long or short rest.