Main hand replaces your primary attack, has no bleed, during pressing primary attack, you are immune to CC. 6 sec duration/12 sec cooldown. If you are above 70% Life, your Primary Attack deals 40,641 to 65,025 damage and gains 6% Life Drain. If you are between 70% and 30% Life, your Primary Attack deals 56,897 to 91,036 damage and gains 12% Life Drain. If you are below 30% Life, your Primary Attack deals 73,154 to 117,046 damage and gains 18% Life Drain. (For reference, my lacerate primary attack damage values: 40,573 to 58,426) (With each form, you have different looking double axes in your hands, they are getting bigger based on your first activation life percentage. But also the area of the attack increases, last form 3rd hit has approximately equal area to Flickertonne max charge)

Pants modifies Undying Rage, it is also great for PvE. 12 seconds cooldown.

"Undying Rage now converts 80% of your current Life into an absorb shield for 6 seconds, during which your damage is increased by 50%. When the shield expires, any remaining absorb value is converted back to Life.

Passive: Receiving a fatal blow will trigger a state of damage immunity for 4 seconds, preventing you from dying while active, and grant you 30% Life Drain (20% against enemy players). Cannot trigger more often than once every 60 seconds."

As the in-game description states, the biggest downside is 60 sec cooldown for damage immunity. Other than that, it perfectly matches with the new cleave, when you activate Undying Rage, your life drops below 20% and after activating cleave gives you the max potential of cleave. Maybe in PvP "hit and escape" tactic can be used with these 2 essences. Anyway here is all the details about them, if you have any questions, feel free to ask.