Sigil Mastery

Outside of Combat you can etch a known spell onto your skin in the form of Sigils of Creation, doing so take 1 hour per sigil. You can inscribe onto your body a number of Sigils of Creation, up to your proficiency modifier number. You can also Etch a Known Spell onto a incapacitated or willing creature in the same fashion as well as an object that can hold magic well. 

These sigils inscribed onto your body can only be removed by dispelling the Sigils of Creation, using the Dispel Magic spell being cast at the same level as the spell that was inscribed in the Sigils. 

While Inscribed on your body, the Sigils of Creation removes access to the spell slot used to cast the spell that is inscribed by the Sigils (I.E if you inscribe the spell "Gate" on your body, you are unable to use that 9th level spell slot until it is removed) 

When inscribed on your body, any and all Sigils of Creation allow you to FREELY cast the spell without using a spell slot, AND these spells cast by the Sigils do not required concentration. 

When a Warlock takes this feat, they can craft sigils freely using their Pact Magic as a catalyst but with slightly differing effects, such as the spells that are Sigiled will only be able to be cast a number of times equal to the characters Proficiency Bonus individually for each sigil. After casting the number of times for the sigil it needs to cooldown and refresh over 2 turns or 12 seconds.

A cantrip inscribed on a creature or object may use that cantrip as a free action out of combat and while in combat, they are allowed to cast that cantrip as a free action once per turn (i.e use action, bonus action and then sigil free action cantrip, is a valid move order).

When an Enchantment, Transmutation, Abjuration, or Illusion spell is inscribed on your body using the Sigils of Creation, the effect of the spell remains active permanently (although certain spells in the category cannot be inscribed due to the permanence of the spell breaking the laws of reality, such as "Invulnerability") 

When a Necromancy, Evocation, Conjuration or Divination Spell is inscribed on your body using the Sigils of Creation, The effect of the spell can be called upon freely out of combat, or as an attack action during combat (I.E the spell "Fireball" inscribed on a palm could be cast twice in a combat if the user has more than one attack, spells that cannot be inscribed are ones such as Wish)