What nation(s) are best for fire? (Besides Abysia)

[Managarm]

Sorry, but I forgot to say that Flaming Weapons also adds the chance to set the defender on fire, giving an extra punch of excruciating pain...

A unit on fire takes 1-2 points of AP damage per turn until fire extinguishes, and it takes longer to go out in warm dominions.

[Managarm]

Astral path seems a good candidate to Marignon since their initial sites add +4 Fire gems and +1 Astral gem per turn, and it is very good in the long run.

A high Astral rating also unlocks their mighty National Summons, although some Arcane Probing (Evo 2)/site searching should be done beforehand due to the high number of gems required per summon.

[B0rsuk]

Another advantage of Fire compared to Blood for Marignon:

Knight of Chalice
Hoof is 'strength not added' weapon.
Lance is 'strength not added' weapon.

These weapons won't benefit from extra strength, but Flaming Weapons will most likely still work.

[llamabeast]

Flaming hooves! Good point, I wouldn't have thought of that.