The potency of your Eldritch blood was always unlimited in scale, the percent of your blood that was Eldritch however was locked. Now that has changed, the percentage has been significantly upped and your magic/Eldritch power has dramatically increased. Your magic power and the power of your blood and its enhancements is increased by 5 times and every subsequent improvement in potency is 5 times what it would have been. You also gain an instinctual understanding of Eldritch spells, summons, rituals and Blood spells, enhancements and rituals as well as immediate access to several of spells and rituals in every category mentioned including normal magic (6 spells and 6 rituals per category) all of which are useful to you in one way or another.
Pthumerian
Your blood percentage is increased once again, matching those directly related to Great Ones demi-divines if you will. Your magic/eldritch power is once again enhanced by 5 times(Total stack of 25x base power in these stats) and so are all subsequent potency enhancements. You gain access to every spell/ritual mentioned in game and lore including things like the Augur and A Call Beyond and the like, you also gain 44 more spells and rituals in all categories. You are naturally at least neutral to all Eldritch creatures lower than Great Ones and even they are naturally drawn to you, you may summon/intimately contact 1 every 24 hours for free magically speaking and they will always at least hear you out before making the call.