I went on this normal server but it was changed to be hard. There where meteor showers, diseases and big mobs. I had no mods installed it was a normal IP but there where big mobs. How do I do this on my server? Is it a plugin or what? I had no mods install client side.
The only 'big' mobs you can see with an unmodded client are giants, a large version of zombies. They don't spawn naturally and you need a server mod/bukkit plugin to spawn them.
idk if these are any good but heres wat i got after a glance at the plugins list: AdvancedMob - that should handle your "big mobs" as you can make giants spawn naturaly NeoMeteors - theres your meteors, i used this plugin a while back but it destroyed my worlds too often as for the sickness just eat some rotten flesh or try a vampire plugin
