Elderseal Rework is a mod that changes how Elderseal works on all the elder dragons such as Kushala, Teostra, Lunastra, Kirin, Vaal, Nergigante, Velkhana and Namielle.

It's a great way to get feedback from the monsters you're hunting, as the monster's health will be visible to you. 
The feedback is similar to how a monster's health drops when you use a special attack, but the difference is that the feedback is visual and immediate as it will now nuke the monster's aura or armor by completely.

In addition, Xeno'jiiva and Safi'jiiva had their numbers rearranged to allow for Elderseal to be a viable weapon choice.