Elmon's ambassador

Choose one corpse of Medium or Small humanoid within range. It becomes Ghast with the following modifications:

• Hit point maximum is increased by an amount equal to your level.
• Has Multiattack property: The Ghast makes two attacks with its bite or with its claws.
• Ghast use your proficiency bonus Instead of Ghast's for attack rolls and Ghast's attacks deal an extra damage equals your proficiency bonus.
• Ghast's Turning Defiance property affecting all undead creatures under your control, not only ghouls.

Once casted, spell transfers your soul in created Ghast and you gain full control of it. Your body falls into a catatonic state and can't regain hit points until your soul returns.  Your body takes 5 (1d10) necrotic damage on the end of every hour while your soul out.

In order to return your soul you can use your action and must succeed on a spellcasting ability contest against Ghast's wisdom. In the end of every hour after casting a spell Ghast gains +1 bonus to his check. You can do this once in hour.

If Ghast is killed your soul returns to you body if the body is alive. If your body is dead when you attempt to return to it, you die. Once your soul leaves Ghast's body, It becomes independent and follow Ghast's instinct to form pack of ghouls.

As a Ghast you can't cast spells, but you maintain your attunments, can use magical items and maintain control of any creature you had before casting a spell (such as Find Familiar or Animate Dead).