Who is Elogio Santillanes from Talking God and what is their importance?

Elogio Santillanes is the murdered man dressed in worn but expensive hand-tailored clothes and pointy shoes whose body is dumped in the desert is Old Man Santillanes. Uncovering the man's identity is further complicated because he uses the alias Hilario Madrid-Pena while traveling. Lieutenant Joe Leaphorn is first drawn into the investigation by Santillanes' murder.