inner circle
A small, exclusive, and intimate group of like-minded people sharing a common goal, pursuit, or purpose. After nearly 20 years working for the company, I was finally brought into the board of directors' inner circle. John, Samantha, Mary, and I are kind of the inner circle of our wider group of friends.
inner core
The innermost part of something. The term is used both literally and figuratively. What is the Earth's inner core made of? At his inner core, he's a good person, I just know it.
inner strength
One's resolve or determination. You have to draw on your inner strength—it will carry you through an experience like this.