The Noble ability has only one level - there is no such thing as "Super Noble". On the other hand, the higher the Hero's Upkeep Costs would've been without this ability, the more valuable it is for that Hero, since it saves more money.
The majority of Heroes are, in simple terms, mercenaries plying their trade. They'll work for you, but only as long as you pay them for the effort. However not all Heroes consider their deeds a "job". For various reasons, a Hero may decide that your cause is just, and ask for no compensation.
In fact, such Heroes are often so devout that they will contribute whatever donations they receive or whatever treasures they acquire directly to their employer. Even the most evil Heroes may occasionally do so - presumably because they believe their employer's ultimate goals (known or otherwise) will benefit them in the long run.
The Noble ability is quite simple compared to other abilities.
Instead, at the start of each and every turn while the Noble Hero is under your employ, he/she will contribute exactly 10 Gold directly to your treasury. Therefore, instead of taking payment, the Hero pays you.
The higher the Hero's default Upkeep Costs, the more valuable the Noble ability is for that Hero. For example, a Hero who normally requires 4 per turn instead gives 10 per turn, so the total benefit from the presence of the Noble ability is +14. If the Hero would normally require 10 per turn, the total benefit from Noble would be +20.
This extra income can be very welcome, especially during the early game. Remember that you only get the extra Gold while the Noble Hero is alive and under your employ. If he/she is killed off or dismissed, the extra income disappears. It is therefore usually a better idea to keep Nobles away from combat.
Improvement Table Edit
Heroes with Default Noble Edit
There are exactly 3 different Heroes that possess the Noble ability by default each time you play the game:
Of the above, B'Shan is the only Non-Champion. He is so weak overall that most players will only hire him for the Noble ability, which can boost income significantly during the early stages of the game.
Noble as a Random Ability Edit
The Noble ability is found in all Random Ability categories. Any Hero with at least one Random Ability pick that does not already possess Noble may occasionally acquire it at random. There are no fewer than 24 different Heroes in the game that may do so:
* It is currently unknown whether Torin can actually acquire the Noble ability, and what this would do to his Upkeep Cost, which is paid in Mana rather than Gold. More information on this would be welcome.