Arcane Reagent

Amorphous. The reagent can move through a space as narrow as 1 inch wide without squeezing.

Magic Absorption.  The reagent has advantage on saving throws against spells and other magical effects.  When the reagent is subjected to the effects of a spell, it gains temporary hit points equal to 1d10 + the level of the spell.

Spider Climb. The reagent can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Multiattack.  The arcane reagent makes two attacks with its pseudopods.

Disgorge Magic.  The reagent expels stored magical essence.  Each creature within 30 feet of the reagent must make a DC 14 Dexterity saving throw.  On a failure the creature takes 27 (6d8) of either cold, fire, or lightning damage (the reagent's choice).  A creature takes half damage on a successful saving throw.

Pseudopod. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage plus 7 (2d6) acid damage.  If the target is a creature with spell slots, it must make a DC 14 Constitution saving throw.  On a failure, one of the creature's 1st-level spell slots is immediately expended, absorbed by the reagent.  If the creature does not have spell slots, or has no remaining spell slots of 1st-level, it automatically succeeds this saving throw.

Nullify.  When the reagent is subjected to the effects of a spell of 5th level or lower, it may use its reaction to nullify the magic, absorbing the magical essence into itself.  The spell instantly fails and has no effect, and the reagent gains temporary hit points from the spell as normal.