Blessing of Tiamat

You speak mentally with Tiamat and conduct a ritual. 

You bless one creature. If that creature is a Chromatic Dragonborn or a Dragonkin who is evil or follows Tiamat, then apply the following:

The person gains immunity instead of resistance to the element of their breath weapon.

The person may choose whether to use their breath weapon in a 15 ft. cone or a 30 ft. line each time they uses their breath weapon, increasing the length by 5 ft. every 5 levels.

The person may choose what saving throw the target/s of their breath weapon has\have to do when they use their breath weapon, making the saving throw DC harder by 1 every 5 levels.

Additionally, the person may change the colour of their scales and the colour of their breath weapon to any Chromatic colour, but they may not change the element of their breath weapon or the element that they are resistant/immune to.

If the creature is not a Chromatic Dragonborn or a Dragonkin who is evil or follows Tiamat, then apply the following:

The person may choose to have their skin replaced by scales and have resistance to a Chromatic Dragonborn element of their choice. They may change the colour of their scales to any Chromatic colour, but not the element they are resistant to.

The person gains a breath weapon of a Chromatic Dragonborn element of their choice. They may change the colour of their breath weapon to any Chromatic colour, but they may not change the element of their breath weapon.

All choices can be changed every long rest.

Cannot be dispelled except by Tiamat