RTF is a global modification that replaces all towns in the game.

well, here’s my vision of how the Faction could be reorganized if we use Sea Elves as well:
Tier 1: “Frogs” – tamed beasts
Tier 2: “Sea Elf Archers”
Tier 3: “Shark Guard”
Tier 4: “Water Spirits”
Tier 5: “Priestesses”
Tier 6: “Nagas”
Tier 7: “Giant Water Elementals”

Added 9 minutes later
or we could do it like this:
Tier 1: “Frogs” – tamed beasts
Tier 2: “Sea Elf Archers”
Tier 3-4: “Shark Guard”
Tier 4-3: “Lake Nagas – warriors with shields”
Tier 5: “Priestesses”
Tier 6: “Water spirits or some kind of flying sea creature”
Tier 7: “Giant Water Elementals”