Replace faction.

I'm hearing about level-based restrictions for the first time; I was told that if I replaced the wyvern with a manticore, it would start working, but that's the path of someone creating custom maps.

Added 12 minutes later
I gave the wyverns bonuses and assigned them to Tier 5, but it didn't work. I'm actually a little glad because I'm planning to move the naga to Tier 6, so nagas don't have bonuses because they're a cursed race.