WHhy does this error happen with 2.5.0

Everytime i load my server with mm 2.5.0 on it i get this

[05-08-2016 14:21:03] Could not load 'plugins/MythicMobs-2.5.0.jar' in folder 'plugins'
[05-08-2016 14:21:03] org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: net/elseland/xikage/MythicMobs/MythicMobs : Unsupported major.minor version 52.0
[05-08-2016 14:21:03] at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[spigot.jar:git-Spigot-9797151-301db84]
[05-08-2016...

WHhy does this error happen with 2.5.0