Hammer Catalyst is a high damage duelist; its DPS on top of boon support from Depth of Elements allows it to be great even in larger fights where Elementalist typically suffers.
Unlike typical Elementalist builds, hammer has a high focus on mitigating incoming damage rather than resustaining through it. Your best defensive skills are Fortified Earth, Conjure Earth Shield, and Immutable Stone. Upkeeping auras specifically Shocking Aura and Magnetic Aura significantly boost your sustain in most matchups, and frequently comboing into them can even win certain duels by themselves.
Deploy Jade Sphere makes catalyst tick, your success will vary widely based upon how much energy you have and are generating. You won’t be getting auras, Stability, or condition removal without comboing through your jade spheres. Engaging with Conjure Earth Shield is a great way to build up energy when you don’t have any while keeping yourself safe. When you’re at your most vulnerable without energy, try to swap through your attunements while you’re holding your Conjure Earth Shield for additional energy.
Most of hammer’s damage output will come from the Fire Attunement skills, however hammer can do noticeable damage outside of Fire Attunement too with skills like Hurricane of Pain and Cleansing Typhoon, and Conjure Earth Shield auto attacks. Standing close to enemies with your Hammer 3 orbs up also does sizable damage and generates a significant amount of energy, but is inconsistent due to the projectiles getting blocked or destroyed.
As mentioned earlier, hammer catalyst focuses on mitigating incoming damage rather than just resustaining through it with water combos and the more you do it will boost your offensive capabilities.
Fortified Earth is a 3 second block that also will give you 3000 barrier to deal with whatever is thrown your way after the block expires. You can lower the recharge on Fortified Earth to a very low 16 second cooldown by casting Deploy Jade Sphere before or during Fortified Earth’s channel.
Anytime you get an aura you’ll cleanse a condition thanks to Smothering Auras. This is the way you keep conditions off of you when they’re applied slowly to you over time. The best way of dealing with a condi bomb is either Cleansing Typhoon which can cleanse anywhere from 2 to 6 conditions although usually 3-4, and Conjure Earth Shield’s #5 skill Fortify as most conditions will fall off during the 3 second invulnerability.
As mentioned earlier, resetting your Fire Attunement skills is great at helping you get a kill, but when chasing down enemies with your teammates, it can often be better to set them up for success by resetting Air Attunement skills to chain crowd control with Wind Storm and Shock Blast.
Crashing Font will only heal you a lot if you hit a target with it; to avoid this being nullified by Blinded or Aegis you can use a jade sphere during or before the cast of it to remove those two effects. You can also use Signet of Air to blind enemies during the cast to keep yourself from being interrupted.
Swapping your Rune of Divinity to Rune of Speed can help you chase down kills if you find yourself sidenoding less or if you expect to sidenode less.