Adult Fantasy/Sci-fi book in a series, Magic and Shifting elements, Hero is an old warrior accompanied by friends and important woman (possibly a princess/queen) who can shift into cheetah or leopard

[Hilma]

I read this book in the early 2000s, but I believe it was written a decade before that. I don’t remember much of the story other than an old warrior (maybe ninja) is helping to save a kingdom with a group of his friends and either a princess or queen who can shift into some type of cat. What I remember most is the cover. It was light blue or teal. I think the title was a larger font and possibly yellow in color. The man was on the cover. It was a picture of his face, older with shoulder length greying hair and a cheetah or leapord in the background. I think the author’s name could have been David and his last name may have started with a C. This book is part of a long series and it may have been the last book.