Shapeshifter's nature (updated)

Prerequisite: Changeling race, Dexterity 20

you have become a master over your physical being.

You are now immune to diseases and poisons, effects that cause advancing or the reversing of aging, have advantage against spells that force changes to your physical form, and have an increased lifespan. For every 5 years of aging you age as if only 1 had passed.

In addition you can now change your form as if you have cast the Polymorph spell. If someone tries to dispel this effect with Dispel Magic you gain advantage on your saving throw.