What's the abstract noun for 'deserve'?

Is there an abstract noun for 'deserve'? If not, is there a criterion for words to have an abstract form?

For example, say I am creating a game where I need my character to gain some "Co-efficient of (abstract noun for deserve)" to access something.

In this context, I think this would suit your character's description:

Merit - MW

A good quality or feature that deserves to be praised
The quality of being good, important, or useful : value or worth

For an in-game character, deserve is too vast. You have to wonder how and why he deserves something (like to enter a new zone, or to get a new aptitude) before actually putting a noun on it.

See: http://www.collinsdictionary.com/dictionary/english-thesaurus/merit, goodness, virtue, integrity, talent are all features that could make your character deserve something.

There is an abstract noun from 'deserve': 'desert' (Chambers). This is often encountered in the plural (e.g. "just deserts").

I'm not suggesting it (or anything else) for a computer game, but you did ask.