Each time you activate a special attack while you on the Raggadorr's Resolve Blessing, you will gain a Rune of Raggadorr (Blue one). An SP1 will give you 2 and then will spend 1, an SP2 will give you 3 and then spend 1. Activating an SP3 for the first will grant you a permanent rune. Each time this rune is consumed you activate the 75% block on hit regeneration plus you'll regenerate around 500 health over 12 seconds. You can stack the regeneration.