Keys to the Kingdom noun phrase
A resource that will allow the possessor to access to power, knowledge or understanding
Man, I really appreciate you for giving me this book. It's like the keys to the kingdom of knowledge.
Those books I gave you last week are the keys to the kingdom. Read them and you will know what I mean.
If you want to have the keys to the kingdom, you must have the support of the president.
The most important or influential part of a group or organization
That which enables one to discover or get access to something good or desirable.
This phrase originated from the concept that resources were the means of obtaining control over an actual kingdom. It's also a reference to Matthew 16:19, when Jesus said to Peter:
"I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven."