EDIT: Also happens with regular Spigot 1.8.8 - not exclusive to PaperSpigot
Using PaperSpigot 1.8 (4c7641d) to be exact - the plugin fails to load with the following exception:
[Duels] Enabling Duels v3.4.0
[Duels] Successfully hooked into 'Essentials'!
[Duels] Successfully hooked into 'Factions'!
[Duels] Successfully hooked into 'PvPManager'!
[Duels] Successfully hooked into 'Vault'!
[Duels] Successfully hooked into 'WorldGuard'!
[Duels] There was an error while loading KitManager! If you believe this is an issue from the plugin, please contact the developer.
[Duels] Disabling Duels v3.4.0
[Duels] Disable process took 5ms.
WARN [Duels] Task #1319 for Duels v3.4.0 generated an exception
INFO java.lang.IllegalAccessError: tried to access class me.realized.duels.duel.DuelManager$DuelListener from class me.realized.duels.duel.DuelManager, at me.realized.duels.duel.DuelManager.lambda$new$46(DuelManager.java:108) ~[?:?]
EDIT: Also happens with regular Spigot 1.8.8 - not exclusive to PaperSpigot Using PaperSpigot 1.8 (4c7641d) to be exact - the plugin fails to load with the following exception: