Being immortal might sound ideal—no wrinkles, no existential angst, or fear of death. But a character who is secretly living forever will have many challenges. Their methods for keeping this information quiet will likely change over time—unlike their apparent age.

Powers or Abilities (primary)

LIVING UNDER A CURSE, PRACTICING WITCHCRAFT

ABANDONMENT, BEING ATTACKED, BEING LABELED, BEING SEPARATED FROM LOVED ONES, BEING TAKEN ADVANTAGE OF, BEING WATCHED, BETRAYAL, CONDITIONAL LOVE, CONFLICT, ISOLATION, LOSING AUTONOMY, LOSING ONE'S SOCIAL STANDING, NOT BEING BELIEVED, PERSECUTION, REJECTION

Avoiding getting attached to others because the character will always outlive them
Fearing rejection or becoming an object of hatred, envy, or fear if the secret gets out
Having to project a maturity level that matches the seeming age of their body (if they became immortal at a young age)
Losing their sense of self after centuries of changing identities 
Being unable to affect change at high levels because the visibility would compromise their secret
Underestimating mortals, leading to arrogance and an inability to empathize
Losing their moral center over time
Having to avoid activities that could result in scrutiny of their blood, skin tissue, or anything that would draw suspicion

Moving frequently to hide the fact that they don't age
Changing identities and appearance on a regular basis
Faking their deaths when they want to adopt a new identity
Resurfacing every generation as a younger relative of their former identity
Accumulating enough wealth to withdraw from normal society and pay people off if necessary
Killing anyone who discovers the secret