Mislead

When a mislead spell is cast by the illusionist, he or she actually creates a phantasmal double at the same time that he or she is cloaked by improved invisibility magic. 

The illusionist is then free to go elsewhere while his or her phantasm seemingly moves away. The spell allows the phantasm of the illusionist to speak and gesture as if it were real, and there are full olfactory and touch components as well. 

A detect illusion, true seeing or true sight spell, or a gem of seeing, will reveal the illusion for what it is, and a detect invisibility, true sight, or true seeing spell, or a gem of seeing or robe of eyes, can detect the invisible illusionist (cf. shadow door).