Dracomorph

This spell transforms a creature that you can see within range into a dragon species of your choice. An unwilling creature must make a Wisdom saving throw to avoid the effect. The spell has no effect on a shapechanger, a dragon, or a creature with 0 hit points.

The transformation lasts for the duration, or until the target drops to 0 hit points or dies. The new form can be any dragon whose challenge rating is equal to or less than the target's (or the target's level, if it doesn't have a challenge rating). The target's game statistics, including mental ability scores, are replaced by the statistics of the chosen beast. It retains its alignment and personality. A transformed target cannot use their dragon form's legendary actions.

The target assumes the hit points of its new form. When it reverts to its normal form, the creature returns to the number of hit points it had before it transformed. If it reverts as a result of dropping to 0 hit points, any excess damage carries over to its normal form. As long as the excess damage doesn't reduce the creature's normal form to 0 hit points, it isn't knocked unconscious. However, when the target reverts to its original form it must make a Constitution saving throw. On a failed save rather than reverting to their original form the target's race changes to Half-Dragon. If the target is a dragonborn, their HP drops to 0. 

The creature is limited in the actions it can perform by the nature of its new form. They could understand and speak in Draconic, but cannot speak in Common. They could not use any spells they had in their original form. 

The target's gear melds into the new form. The creature can't activate, use, wield, or otherwise benefit from any of its equipment.

This spell is also known as Erason’s God Damned Polymorph.
2nd Version: The spell is now an 8th level spell.