Arcane Copycats have an innate ability to attune with magical energies around them and use them for their own needs.  This can apply to other magic users or to magical items they may find.  Arcane Copycats will use their abilities to track and find powerful mages or wondrous items to make themselves as powerful as they can.  

Copycat

The Arcane Copycat can view a spell being cast within 120 feet and roll an Arcana Check (DC = 10 + Level of Spell).  On a success, the Arcane Copycat may switch that spell with one of their known spells, so long as it is within their ability to cast.  (Example, if Cure Wounds is cast at a 4th level spell slot, the DC to know the spell is calculated as if the spell was a first level spell as the spell Cure Wounds is itself a first level spell.  Cantrips have a DC of 10.)  The new spell learned is retained for the Arcane Copycat regardless of what class the spell belongs to.

Channel Arcana

Once per long rest, as an action, an Arcane Copycat can channel the arcane energy from one object and temporarily imbue another similar object with the same ability.  The caster must touch two similar objects (two martial weapons, tool sets, pieces of armor, etc.) and copy the enchantment of the magical object to the non-magical object for one hour.  This duration increases to 24 hours at 6th level.

Arcane Feedback

If another caster is within 60 feet of the Arcane Copycat, the Copycat can use their reaction to impose disadvantage on a saving throw to resist magic or to a magic spell attack.  This can be done up to an amount of times equal to the Arcane Copycat's Charisma ability modifier.

Arcane Resiliance

The Arcane Copycat has advantage on saving throws against magic.

Arcane Removal

Once per long rest, the Arcane Copycat can target another spell caster within 30 feet and make an Arcana check against the target's spell DC.  Upon a success, roll 1D10.  The target loses that many levels of spell slots, gains one level of exhaustion, and the Arcane Copycat gains that many levels of spent spell slots.  (Ex: on a roll of an 8 on the D10, the spell slots can be lost as two 4th level spell slots, four 2nd level spell slots, or one 8th level spell slot.  Spell slots can be replenished for the Arcane Copycat in the same way.)