'This... power, no, this isn't... it can't be human!' 

While this spell is active you may, as an action, alter your physical form in a one of the following ways- mutating yourself in an unnatural, horrific manner. As an action, you can transform into a terrible monster- your body changes and warps in structure, and you are practically unrecognizable from your normal form. You can also, as an action, end this transformation. While altered in this way; you suffer disadvantage on all Charisma Checks ( Except Intimidation ) and Charisma Saving Throws, you suffer a -5 penalty to Persuasion and Performance. The transformation lasts for a minute total. Depending on the level of the spell, you take an amount of transformations listed ( you cannot take the same one multiple times ) equal to the level of the spell slot ( Maximum of 6 ). 

You can only have one instance of this spell active at a time, and once you learn this spell- your body is permanently altered, something which can be determined by a creature with an Insight check ( against your Deception ) as an action, if they succeed- they are aware you are something other than your natural form. If they are a spellcaster, they may instead make an Arcana check ( against your Arcana ) as an action, if they succeed- they determine you haven taken this spell and have undergone this transformation. The following transformation options are available:

• Eye of Mystra: While this transformation is active and you are conscious, you gain a +5 bonus to perception checks for the duration as multiple sets of eyes sprout from all over your body. 
• Mouth of Mystra: While this transformation is active, you gain an unarmed strike ( 1d6 + Spellcasting Modifier Damage ). You may also, as an action, consume and eat a creature of large size or lower that is at 0 HP or unconscious- If you do so, you can heal an amount equal to ( Proficiency Bonus + Spellcasting Modifier ). A horrific, gaping and toothy mouth opens up from the bottom of your stomach to your chin. 
• Tongue of Mystra: While this transformation is active, you may make a grapple check against a creature against you within 10ft as a bonus action or reaction when an enemy leaves 10ft of you. Your tongue grows up 10ft long, and spirals out of your mouth with a large blade at the end. 
• Spines of Mystra: While this transformation is active, you gain natural armor equal to ( 10 + Proficiency Bonus ). You cannot wear armor or clothing while this is active, as large spines grow all along your spin and forearms.
• Limbs of Mystra: While this transformation is active, your movement speed increases by ( Half of your Proficiency Bonus [ Rounded Down ] x 5 )
• Guts of Mystra: While this transformation is active, you gain resistance to poison damage and become immune to disease. Gaining this transformation does not cure any disease you have at the time.

If you are transformed into a creature or object by another spell during this duration via Polymorph, True Polymorph, Flesh to Stone, or another similar spell you can retain the transformation effects until the duration is over. If you do not have movement speed, you do not get the benefits of 'Limbs of Mystra'.