There are two builds paths for Jax, there is the famous Tri-force/Warmog/Atma's Impaler. But there is also the Frozen Mallet/Warmog/Atma's Impaler build also. Depending on the situation, whether to pick Tri-force or Frozen Mallet depends if you are being focused or have a hard time with survivability. A Tri-force provides much more damage and Movement speed, but frozen mallet provides a much larger HP boost, AND a perma slow. Atma's impaler also scales better with the Frozen Mallet.