Through years of practice, you have developed the ability to alter your form in beneficial ways. You are able to selectively modify your body to allow you to improve certain statistics and abilities. You may select no more than one of the following at a time--all of them reveal your identity as a changeling to anyone observing you.

• Lengthen and strengthen your legs/expand your lung capacity - increase your base speed by 10, advantage on Con checks or rolls vs exhaustion due to running.
• Choose one of vision or hearing - gain advantage on perception or related rolls using the selected sense, and disadvantage on rolls using the other.
• Lengthen your arms - gain Reach for melee combat, lose any dexterity bonuses to AC. 
• Choose one of Strength or Dexterity - gain a +1 modifier to the chosen ability, suffer a -1 modifier to the other. 
• Create webbing on your hands and feet - gain swimming speed equal to your base movement rate, provided your hands and feet are uncovered.
• Extend and strengthen your fingers and toes, lengthen your arms and legs - gain a climbing speed equal to your base movement rate, provided your hands and feet are uncovered.
• Extend and narrow your torso and head - gain the ability to squeeze into spaces restricted to Small (but not Tiny) creatures.