Arcane Rune

You inscribe your personal rune upon a book, map, scroll or other object bearing written information, such as a crate. The rune must fit within 1 sq. ft. and can be visible or invisible. If an invisible rune is made, a Detect Magic will cause it to glow. An arcane rune can be removed by the caster at any time by touching the rune as an action.

When you place the rune, you can choose to have it harm creatures that read the text that don't meet chosen characteristics, such as a certain creature kind, an affiliation, or an alignment. Any illicit creature that starts reading the text—which requires the Study action in combat—must succeed on a Intelligence saving throw or take 1d4 Cold, Force, Lightning, Necrotic, Psychic, or Radiant damage (your choice). On a successful saving throw, a creature takes half damage. 

You can have an unlimited number of harmless runes, but you can only have a number of harmful runes active at a time equal to 1 + your character level. When you reach 5th level, a triggered rune also alerts you with a mental ping that a forbidden creature has tried to read the written object while it's on the same plane of existence as you.

Cantrip Upgrade. You can choose to increase a rune's damage by 1d4 when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4).

Adapted from the AD&D 1st edition spell Arcane Mark