I'm really struggling to pick as well.

I'm down to either Cthulhu, Mammon, Asherah or Svarog.

Right now I've got Amaterasu, Mars, Uriel, Ares AW for fire.
Brahma, Raiko, Tyr, Thor AW for lightning.
Ryu-oh, Snow Raphael, Shiva, Aphrodite, Atalanta for water.

I'm leaning slightly towards Mammon for lightning, but am also wondering about just assigning them numbers and rolling a D20.

Thanks in advance for any advice.