Not all mimic variations come to their current state due to their own desires and evolution. The bibliophile mimic, for example, comes from the meddling of a possibly-mad wizard. In this case, the wizard wanted to ensure that his grimoires, scrolls, and personal papers were well protected. To that end, he layered enchantment after enchantment upon a tamed mimic. The resulting monstrosity not only could leech off the power of spell books on its shelves but also become smart enough to sling those very same spells in defense of its wares. Over time, the mimic had offspring which the wizard traded to allies and rivals for various magic wares. Now it is not uncommon to see these variations across the realm. As for the first bibliophile mimic, most say that while its creator is long dead, the monstrosity lives on. It now inhabits and controls that wizard tower, creating clones and emissaries to keep up the cover of an archmage.

Bibliophile Mimic

Medium monstrosity (shapechanger), neutral

Armor Class 16 (natural armor)

Hit Points 90 (12d8 + 36)

Speed 15ft

Str 18 Dex 12 Con 16 Int 18 Wis 13 Cha 8

Skills Arcana +7, Stealth +7

4 Damage Immunities acid

Condition Immunities prone

Sensesdarkvision 60 ft., passive Perception 11

Languages understands Draconic but cannot speak

Challenge 5 (1,800 XP)

Shapechanger.

The mimic can use its action to polymorph into a sturdy bookcase or back into its true, amorphous form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Adhesive (Object Form Only).

The mimic adheres to anything that touches it. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 15). Ability checks made to escape this grapple have disadvantage. The mimic can activate and deactivate this ability as a bonus action.

Conditional Magic Resistance (Object Form Only).

The mimic has advantage on saving throws against spells and other magical effects as long as it has a spellbook or scroll sitting on its shelf that has been there for at least 24 hours.

False Appearance (Object Form Only).

While the mimic remains motionless, it is indistinguishable from an ordinary sturdy bookcase.

Grappler.

The mimic has advantage on attack rolls against any creature grappled by it.

Innate Spellcasting.

The mimic can innately cast Minor Illusion (spell save DC 12), requiring no material components. Its innate spellcasting ability is Wisdom. The mimic can only produce sounds it has heard with this spell, most often funeral poems, speeches, weeping, confessions etc.

Actions

Multiattack.

The mimic makes two pseudopod attacks.

Pseudopod.

Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite.

Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 4 (1d8 + 4) piercing damage plus 9 (2d8) acid damage.

Cast Spell (recharge 5-6) (Object Form Only).

The mimic casts an arcane spell of 4th level or less contained in either a spellbook or spell scroll which ahs set on its shelf for at least 24 hours and that takes an action or less to cast. No matter the spell's class origin, the mimic uses its spellcasting ability of Intelligence (DC 15, +7 to hit with spell attacks.) Once the mimic casts a spell it cannot cast that spell again until 24 hours has elapsed. The mimic forms a Magic Mouth for all verbal components and temporary, tiny pseudopods for somatic components. The spells it casts do not requite spell components of the components are 100GP or less.