I once again suggest to barricade and let them fight each other. Maher will probably deal quite easily with the mud golems.
Also no alliance. Maybe a cease fire once our fight has finished, but I'm not sure if Maher would accept it. He's probably not the type of guy to share. Plus, he's completely evil.
How's Tiberius doing? Make sure he is not overdoing it. Retreat when/if necessary.
Use some of the fire nectar to heal wounded people. We can't grow back hands yet, we swore not to intervene directly and that would count as such, I'm sure.
Right now why not design our afterlife while patiently waiting for grumugga to be annihilated?
I suggest a central volcano, with smaller mountains branching off in five direction, becoming smaller and smaller with the distance, finally becoming hills. The mountains are surrounded by forests, of various essences (pines, oaks, birchs...). But there is also, and mostly, plains filled with wild plants with harmless thorns and flowers. There will be firejackets and every benevolent creature we'll create. Our followers arriving here will find a couple villages, overwhelmed with plants, but never decaying. The plants are never a hindrance here, not restricting movement, not stinging, not poisoning... The animals as well are harmless. Our follower wont need to eat or drink, etc... But can still enjoy it. Basically it's like actual life, but in a flourishing, harmless environment.
Also they have nature and fire boons there, so they can make whatever plant they want grow and light fire wherever they want.
Chaos could be represented with random, yet innofensive, events. Such as sudden weather changes, random wildlife behaviour, unexpected plant growth (your strawberries patch being replaced with delicious fungus overnight for example). The randomnes will never be frightening, at most mildly annoying, but still funny. (when you can handwave away the mushrooms and make your sweet strawberries back, it's not an annoyance. And you'll have something to say at the next feast.)
One last thing: maybe adding "angels". Inspired by Tiberius, with a metallic (but here it's precious metal like gold or silver) "exoskeletton", and inside a living plant thing, burning with harmless multicolor flames, taking the form of beautiful humanoids. Think of the flame atronach from skyrim with plants inside the black armor. They'll serve the deads like kind, joyful maids.