Transmogrify

You transform yourself or another creature to look different until the spell is willingly dispelled or the targeted creature dies. You can seem 1 foot shorter or taller and can appear muscular or weak. You can't change your body type, so you must adopt a form that has the same basic arrangement of limbs. Otherwise, the extent of the illusion is up to you. The creature will even age according to their new appearance.

The changes wrought are almost impossible to detect. For example, casting the spell detect magic would fail to reveal an aura of illusion magic around the targeted creature. However, spells that detect a creature's identify, such as detect evil and good would reveal the true identity of the targeted creature.