The Krystalline Terror

Deep in the Underdark lies a Forgotten Patron, The Krystalline Terror, the being waited and waited for someone who would seem weak but a Good person in general. he then changes their memories and makes them think that he always been there. he then gives them a weapon that would grant them abilities, but that there is always a catch, he then turns them into one of his minions forcing the user to go into a blood lust. only the strong-minded can withstand the Terror's intentions. He hunts only the one with good intentions, Corrupting them and making them his puppet. many can easily break his hold but to get rid of him from your mind is impossible, he tries to change your mind on a thing you think is good for making you think it is evil. once his blade takes you over, your mindset changes to the complete opposite. 

Krystal Takeover

at 1st level, You are given the ability to create an Ice Crystal blade, but in doing so, your body becomes covered in icy crystal shards. this state is indefinite, you must succeed a Wisdom Saving throw (DC 12 + Half of Character Level rounded up) to get out of it. in this state, you temporarily become Chaotic Evil unless already so. you gain Resistance to Cold Damage and Slashing Damage but gain Weakness to Fire Damage and Bludgeoning Damage

you have + 1 to AC and the Crystal Blade deals 2d4 + STR/DEX magic Cold damage

 

Krystalize Fear

at 6th level, When Turning into Krystal Monstrosity, everyone (including Allies) within 20ft of you have to make a Wisdom Saving Throw (DC equal to 8 + your proficiency bonus + your Wisdom modifier) on Fail save, they are Frighten. you gain Advantage on attacks and an extra 1d4 damage dice against the ones who are frightened.

Personal Krystal Caverns

at 10th level. You gain the ability to morph your Krystal Appearance into different element types and abilities every long rest. (Turning = every time you become a Krystal Monstrosity)

Fire Krystal: Krystal sword does magic fire damage. you temporarily gain the Firebolt cantrip when you turn, you have 3 Krystal bombs per turning, as an action you can throw one of them that deals 1d6 fire and 1d6 force damage when thrown at a creature, they have to make a dexterity saving throw (your spell save will be the DC), successful save, they take only the force damage. you are resistant to fire damage but gain a weakness to Cold, you still retain the Slashing resistance and Bludgeoning weakness

Ice Krystal: Krystal sword does magic cold damage. you temporarily gain the Ray of Frost cantrip when you turn, you can throw 3 Krystal shards as an action or/and one Krystal shard as a bonus action at one enemy (each one has their own chance to hit) each one deal 1d4 ice damage + 2. you are resistant to Cold damage but gain a weakness to Fire, you still retain the Slashing resistance and Bludgeoning weakness

Lightning Krystal: Krystal sword does magic Lightning damage. you temporarily gain the Lightning Lure cantrip when you turn, as an action can throw lightning that can chain to another target 10ft away from them, 3d6 to the first target, 2d6 to the second, 1d6 to third, you cannot target the same person if they have already been hit by that same attack and can only use 3 of them per turning.

Krystalline Domain

at 14th level, Once every long rest you can create a 100ft area of Sharp Crystals, it counts as rough terrain and if any creature (including Allies) stays in it at the end of their turn, they have to make dexterity saving throw (your spell DC) on Fail save, they take 1d4 + 2 slashing damage, on success, they take no damage. if a creature (including you and allies) would happen to become prone in that area, they would take 4d4 + 4 damage.