Grom

Spirit Form
Agi- Str- Vit- Int d4 Ale d10 Wil d10
Spirit d4 (rises to d6 after first ceremony, then d8 after third and d10 after fourth)
Perception d6/Detect Supernatural d10, Unarmed Combat d6/Claws d10, Lore d6/Ritual d8

Physical form
Agi d6 Str d12+d12 Vitd12+d12 Int d4 Ale d10 Wil d10
Vulnerable: Iron (m) Monstrous Appearance (d6), Claws d10W, Armor 3W3S
Perception d6/Detect Supernatural d10, Unarmed Combat d6/Claws d10, Lore d6/Ritual d8, Athletics d6/Run D8/Strength feat d12

Grom's appearance is of a boar-headed 12' giant with hooves for feet and clawed hands. After the fifth ritual, he regained a physical body, but not quite full sized.

In the Hellboy comics, Grom is 18 feet tall. He eats the goblin wizard Gruagach, trapping the wizard's soul inside Grom. Hellboy defeats Grom, shrinking him down to midget size with a charm. Later in the series, Gruagach drives Grom's spirit out and takes control of Grom's body to use for his own. The Hellboy RPG suggested an adventure seed for Grom trying to regain full size, but the RPG was published before the later events in the comics, so I changed the adventure to Grom's spirit trying to form a new body.