I would like to add magical tattoos for a D&D campaign in 5th edition.
In 3e (The version that exposed me to D&D), there is the option to add tattoos with magic; They are permanent and can never be lost, but cost twice as much as an item with the same abilities.
However, there are no such rules for magic tattoos in 5e. I am only using the PHB, DMG, MM, XGTE, VGM, GGR, and MTF.
Are there any guidelines for magic tattoos in D&D 5e?
Tasha's Cauldron of Everything has rules for magic tattoos under Magic Items in Chapter 3 (p. 118) for use in D&D 5e.
The needles (which confer the tattoos) may be traded or purchased using normal rules for magic items. The tattoos themselves usually require attunement1 (requirements vary based on the nature of the tattoo.) Once the tattoo is inked, its magic persists despite any defacement or damage to the surrounding skin.
1 The exception is the spellwrought tattoos, which work mechanically like a spell scroll and is thus more like a consumable.