Ink Magi are able to inscribe spells on living canvas. It’s prohibitive but in a world where magic is hard to obtain it can definitely give an edge. It is permanent unless removed by an Ink Magus.
Using it drains a lot of energy from its owner. To cast a spell via magic tattoos one have to spend Hit Dice (without removing hit points):
- level 1 spell drains 1 HD
- level 2 spell drains 3 HD
- level 3 spell drains 5 HD
Remember that magical healing is not readily available in SiT (as explained: here). Spending HD is the primary way to regain hit points. This should prevent (playtesting will tell, in time.) balance-wrecking from this new source of magic. You will have to evaluate carefully if the cost outweigh the benefit.
A short, incomplete, list of tattoo spells with suggested look:
Cost: 250 gp
- Arms of hadar (black interweaved lines on arms)
- Expeditious retreat (wings on ankles)
- Feather fall, self only (wings on back)
- Magic missile (darts on forearm)
- Shield (triangle patterns)
Cost: 500 gp
- Arcane lock (key or set of keys, anywhere)
- Enhance ability (specific animal of ability, only one ability per tattoo! Anywhere)
- Spiritual weapon (chosen weapon: arm, neck, back or chest)
- Web (web: elbow, of course!)
Cost: 1000 gp
- Animate dead (bones, skull and such: anywhere)
- Conjure animals (one animal per tattoo: anywhere)
- Hypnotic Pattern (a spiral: chest, neck or face)
- Lightning arrow (arrow: forearm)
Higher level spells could potentially exists but are unheard of.