Divine favour -- Godly light randomly bestows units of a side the ability to regen health for a time. Edit: forgot about auto-heal. Maybe boosts the healing rate then. Double edit: Light Elf already does this...probably don't want another one... need to spend more time with the current powers I think!
Famine -- maybe just a grander, larger scale form of the Locust horde.
Just reading a little Greek mythology stuff -- apparently Zeus was big on throwing lighting bolts, who'd a thought. Random destruction of a tile or area of tiles caused by a bolt from Zeus.
More specifically mythological stuff -- Norse side. King Högni sets out in fury wielding Dáinsleif the sword that "must cause a man's death every time it is
bared, nor ever fails in its stroke; moreover, the wound heals not if one be scratched with it." Just a more specific "Hero is Born" style event. If a unit is struck by Dáinsleif it they take bleeding damage every turn.
http://en.wikipedia.org/wiki/D%C3%A1insleifOther Hero ideas:
Sigurd wielding Gram or Balmung
http://en.wikipedia.org/wiki/Gram_%28mythology%29Warrior find Hrotti, Fafnir's treasure:
http://en.wikipedia.org/wiki/HrottiMagnus III wielding Legbiter:
http://en.wikipedia.org/wiki/LegbiterLegendary sword Mistilteinn found by fishermen in the stomach of a pike:
http://en.wikipedia.org/wiki/MistilteinnRegin wielding Ridill:
http://en.wikipedia.org/wiki/RidillSkofnung either wielded by Hrólfr Kraki or found in the timbers of a ship:
http://en.wikipedia.org/wiki/Hr%C3%B3lf_Krakiand... you get the idea. Not sure how helpful being this specific is, but if it is then there's plenty more warriors/artifacts etc.