Elijah and Elisha are major figures in the TANAK. Together they performed a number of miracles that prefigured those done by Y'shua. Of equal importance their actions and prophecies figure into the End Times.
Elijah the Tishbite
Elijah, distressed by the behavior of Israel, turns off the rain. The resulting drought sets up the remainder of his ministry.
Jezebel, having co-opted her husband, the king, imported prophets of her own god, Baal. Elijah set up a confrontation with those prophets at Mount Carmel.
As a prophet, Elisha wields the power of God with a confidence and accuracy that seems more like sight than faith. He cures Naaman the Syrian of leprosy in so casual a manner that Naaman does not initially have any faith that the cure will work.
Being a prophet of God was tough duty. Very often powerful people did not appreciate what you had to say and would have you to be slapped around or worse. The Syrian siege of Samaria.
During his time in the cave at Mount Sinai, God gave Elijah a task to perform. It is only toward the end of his ministry that Elisha actually completes it.