Frontline Combat is a modded team based PvP server that feels like squads and battlefield fights.
It runs regular events every week. The server also uses its own custom mods and content and they try to make the quality better each time.
It is Java only and they are looking to grow the player base so more people can join the battles.
Modded Squad PvP With Weekly Events
GG.MINEWIND.NET New Server IPOrigins Event Server With 100 Players
I found a server that runs Minecraft events and they are almost always themed around Origins. They do apps for new events and they also have a modded zombie event in the works that is taking a while.
Most events split players into 2 or 4 teams and each team gets a specific origin. The host says it is over a week but from past events it usually ends up being about 4 days.
The next event is free for all and you get to pick your own origin. They also warn that the rules are more lenient than a lot of event servers so people should read the rules first.GG.MINEWIND.NET New Server IP