Ingress is different than a fury because it is a direct multiplier to weapon damage before calculating all furys etc. (Meaning it is a sizable damage upgrade) An easy way to tell the difference between an Ingress and a Fury is by the way Ingress is used. To use an Ingress one must type in the Weapon name and it lasts until a server change or a logout.
Current Ingresses:
Rogue: Baekho's blade: 1.5x Weapon Damage (Ee San) Blades charm: 2x Weapon Damage (Sam San)
Warrior:
Ingress: ?x Weapon Damage (Level 70) Viper's venom : 4x Weapon Damage (Il San) Dragon's flame: 5x Weapon Damage (Ee San)
Looking at the damage formula:
(((wpn/2)*Ingress + 8.8125 (for rogues/warriors)+ (Might / 8) + (Dam*2.5)) * Fury *Invis * PA Mult * side modifier)
A simple 1.5x Ingress is the equivalent of ~6 Dam while using a Polearm to ~9 Dam while using a Military Polearm.