Homebrew
Dark Form. The Crystal Shade can transform into a shapeless shadow that is immune to all damage except radiant, and it's able to move through surfaces. It can take this form as long as it is not in sunlight. Magic Devourer. Whenever the Crystal Shade kills a caster, its current and hitpoint maximum is rised by one hit die for the next 24 hours as it absorbs the magic, making itself stronger. This effect can stack. Shield of Darkness. While not in sunlight, the Crystal Shade is immune to fire damage, and it gets a +2 bonus to its AC. Spell-Eater. Crystal Shade has an advantage on saving throws against magical effects. When hit by a spell that it saves against and thus does no damage to it, that misses it, or whose type it is immune to, it absorbs the spell. Roll 1d8 to see what happens when the spell is absorbed. 1-2. The spell is spit back at the caster. If it requires a saving throw, it's that of the original caster. 3-4. The Crystal Shade recieves HP equal to the amount of damage the spell would have dealt. If the spell is not damaging, nothing happens. 5-6. The Crystal Shade spits the spell at a random target. If the spell requires a saving throw, it is that of the original caster. 7-8. The Crystal Shade becomes enthralled by the taste of magic, gaining an advantage on its next melee attack roll. Sprouting Darkness. Every 40 hit points the creature loses, there is a 50% chance a Shade Sprout emerges from the seperated darkness.
Multiattack. The Crystal Shade makes three attacks, two with its claws and one with its bite. Claws. Melee Weapon Attack: +8 to hit, reach 5ft., one target. Hit 14 (3d6 + 4)slashing damage and 3 (1d6) necrotic damage. Bite. Melee Weapon Attack: +8 to hit, reach 5ft., one target. Hit 13 (2d8 + 4) piercing damage and 7 (2d6) necrotic damage.
The Crystal Shade can take 3 Legendary Actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Crystal Shade regains spent legendary actions at the start of its turn. Claws. The Crystal Shade makes one claw attack against one creature it can see. Screech (costs 2 Legendary Actions). The Crystal Shade lets out a shrilling screech that chills the bones and pierces the ears of any who hear it. Every creature within 30 feet of it must make a DC17 Constitution Saving Throw, taking 4d6 psychic damage on a failed save, and half as much on a successfull one.
Cities; near strong sources of magic