Devour Spell

This spell can be cast using a spell slot of 1st level or higher.

You use your reaction to attempt to devour a spell. Both you and the spell's caster make Constitution saving throws. The caster adds the level of the spell slot used for their spell to the roll, and you add the level of the spell slot used to cast Devour Spell to your roll. If the caster rolls lower than you, than the spell is successfully devoured. If the spell was cast at a higher level than Devour Spell, then the caster makes their check with advantage, and you make it with disadvantage; the inverse is true if Devour Spell was cast at a higher level..

If the spell is devoured you can immediately recast that same spell at the same level it was originally cast, without material components. If you don't, you regain a spell slot equal to the slot used to cast the devoured spell (or the highest slot available to you, whichever is lower).

If the spell is not successfully devoured, than it implodes inside of you. A second instance of the spell is cast at the same level affecting only you and originating from within your body. Strength and Dexterity saving throws against the spells affects are automatically failed, and you expend a spell slot equal to the slot used to cast the spell (or the highest slot available to you, whichever is lower). Then if the spell is concentration, it immediately disappears. 

If the devoured spell or spell effect is non damaging or has no significant impact for existing inside of you, for example, Silent Image or Bigby's Hand, then the DM may determine the side effects of consuming such a spell, or alternatively, the DM may have you take 1d6 force damage per level of the spell devoured.