I finished a
MiFi^Igni with 3 runes and I really enjoy the lore for this god. I've got quite a few suggestions for tweaks and abilities, so feel free to use or ignore any of them.
There isn't much benefit to staying at high piety, so I think there is some room for improvement here.
There could be a sliding equipment bonus based on your piety. Giving a bonus to AC, accuracy, and damage would help to make up for the lack of combat abilities, which helps to keep up with the other melee gods.
I'm completely making up numbers, but at max piety +7 AC, and +7, +7 slaying sounds nice. This could be only awarded if you are wearing specific items if you want to create a behavior/restriction such as metal armours, but I feel that it would be fine to be universal, since I didn't like discouraging creating dragon armours.
I'm not a fan of the god providing rC-, since it restricts your choice in equipment, which seems like an odd behavior for the equipment-based god.
The fire resistance is nice, and fits the lore. I don't think it should be given as soon as you begin worshipping him, 4* or 5* piety seems like a reasonable choice.
Divine Bellows was really lackluster the one time I tried to use it, since it didn't even move the hydra away from me. I would rather see a
Divine Flames ability, which would act like Conjure Flame. This could be the first ability, given at 1* or 2* piety, and costing 50-100g.
Firebrand weapon was actually nice for my character, since it encouraged using heavier weapons. Unfortunately I didn't earn this until near the end of Lair, so I think it should be given earlier, perhaps being merged with the Divine Flames ability proposed above (when you select your tile).
Using firebrand weapon on enemies was interesting but seemed awkward. It either completely shuts down an enemy or wasn't useful.
I'm not sure that I would keep the ability to apply firebrand to enemies. I didn't artefact my weapon until zot, primarily due to the lack of enchantment on my weapon. The few scrolls I found tended to fail, and I of course wanted to have as high an enchantment as possible. I do think that this is a great skill however, and should also be extended to
"artefact body armour". The list of choices I was given were somewhat lackluster (and would have fit armours better), but that can be improved. Perhaps allowing weapons to be over-enchanted (up to +12,+12), and never decreasing the enchantment level would improve this. 500g seemed somewhat cheap by the time I decided to use it. This could be an altar ability if you want to limit it's use.
To improve upon the fact that you want to encourage users to enchant their weapons and armour as much as possible, I believe that this god should provide
an ability to enchant your equipment. This would work like a scroll of enchant weapon 3 or enchant armour. This could be the second ability, given at 3* or 4* piety, and cost around 200-400g.
TL;DR1* or 2*:Divine Flames: Works like conjure flame but can also firebrand your weapon. ~50g+SmallPiety
3* or 4*:Enchant Equipment: Works like enchant weapon 3 or enchant armour. ~250g+MeduimPiety
4* or 5*:Resist Fire
6*:Artefact Equipment: Works on weapon and body armour. ~1000g+LargePiety
[Piety Level +1]: bonus to AC and Slaying