Wu Tu Gu is not affected by barbarians, hail of arrows, or non-elemental attacks.
Whenever Wu Tu Gu receives fire damage, it is increased by one.
Wu Tu Gu can use armor in conjunction with his abilities.
Wu Tu Gu's abilities work very similarly to Yu Jin's "Heavy Resolve".
"Ratten Armor" offers better protection than the Wood Armor, because Wu Tu Gu is immune to normal attacks. This includes weapon effects of all kinds, most notably the Gender Swords and the Black Pommel. If a female attacks him with the Gender Swords, he does not do anything. The Black Pommel cannot cut through his ability with a normal attack.
If he has the Wood Armor equipped and is hit with fire damage, the damage is increased twice. Once from the Wood Armor and again from "Fear of Fire".