Dragonmorph

The spell caster literally turns himself into a dragon! His AC, HP, physical attributes, skills, saving throws and attacks are the same of the dragon morphed to, but the spell caster retains his mental attributes and the ability to cast any spells he originally was able to cast. He can use a breath attack in any of his turns, but must use a spell slot to do so (the level of the slot is the same as of the needed to morph into the dragon when using Dragonmorph. You may spend a lower level of spell slot to use a weaker breath attack than of the original size of the dragon you are, but not of a stronger one. ). The type of the dragon (colour/metal/etc.) is the same as the one that provided the material component, or the dragon that the character is related to, if material components weren't needed. Plus, the size of the dragon depends on the slot used to cast the spell:

If you used a spell slot of level 5 or 6, you become a Young Dragon;

If you used a spell slot of level 7 or 8, you become an Adult Dragon;

If you used a spell slot of level 9 you become an Ancient Dragon;

The spell may end prematurely if the caster dismiss it with a bonus action, if he is reduced to 0 or less HP (in that case, he returns to his original form and any excess damage carries over onto his regular HP) or if a Dispel Magic or other spells with similar effects are cast in the dragonmorphed. The spell caster may choose to, when the spell ends its duration of 30 minutes, spend a spell slot the same level as the originally used to cast the spell to extend its effects for another half hour, without needing to use another action to cast the spell.