What did God call Abraham when He warned King Abimelech in a dream?

Answer: A prophet

God told Abimelech, "Return the man's wife, for he is a prophet; he will pray for you and you will live."

“Now return the man’s wife, for he is a prophet; he will pray for you and you will live. But if you do not restore her, be aware that you will surely die—you and all who belong to you.””— Genesis 20:7 (BSB)