Dr. Virgil Halifax

Synthesist Summoner; middle-aged half-elf from Cheliax.
Hair: short, greased back, brown and graying, trimmed goatee ;
Eyes: violet-blue, reading glasses.
He tends to wear high-brow suits (usually three pieces and tails) along with a bowler-style cap. He wear a look of kindness, but the bags under his eyes reveal more of the loneliness and horror he's seen. As he tips his hat, he reveals the bastard in his bloodline, transforming into his eidolon, a monstrous winged ape-like demon. In this form, he has beady eyes under a heavy brow and tusks that jut forward in an under-bite. his skin seams almost like stone; the veins in his immense arms could be confused with cracks in his obsidian palor.

I was thinking of him tipping his hat in the foreground and his eidolon behind (Large size) signifying the transformation.