Gelugon

Ice devils, also called gelugons, were the strategists and masterminds of Hell's armies. They made their decisions based on cold, calculated logic, with no thought of the losses of troops. As long as success were possible with their plans, they were willing to sacrifice any number of infernal soldiers.

Appearance
Gelugons appeared to be large, insectile devils that stood on bird-like legs. They carried frozen spears that numbed and slowed the bodies of anyone struck by their pointed ends. A gelugon stood twelve feet tall and weighed 700 pounds.

In the Realms
A gelugon named Vreesar led an attempt to conquer Toril from a portal in the Great Glacier in 1366 DR. He was stopped by a Harper ranger and a fallen paladin.