The vanilla behavior for most mobs is that they just stop minding their targets' business if aggro is lost. The same applies to guardians and elder guardians. To prevent the pace of gameplay from stagnating, MobArena compensates for target loss by helping the mobs find a new target. The issue with this in terms of guardians is that breaking line of sight is the only way - besides killing it very quickly - to avoid taking damage from a guardian due to its lock-on laser attack. This means that guardians and elder guardians need to be excluded from the retargeting logic to make sense in an arena setting. This commit introduces a new EnumSet of EntityTypes to exclude from the retargeting logic. It is not a particularly pretty solution, especially not since ArenaListener is such a huge class already, but it does make it easier to add more mobs later down the road, and it does a slightly better job at giving way to a config setting at some point. For the Mobs Rework, a per-monster flag like `auto-retarget` or similar might be a much better solution, so it's possible to have encounters like a small batch of guardians that _don't_ lose their targets but have very little health, so the "race against time"-aspect can exist, but in a much more configurable way. Fixes #601
MobArena 
MobArena is an arena-style minigame for Spigot-based Minecraft servers
Getting Started
If you don't want to compile the plugin yourself, grab a release artifact from one of these two sites:
The wiki here on Github should have all the information you need to get started using the plugin.
Getting Help
If you run into problems or need help with something, feel free to hop on the MobArena Discord server to have a chat: Instant Invite
Remember, though, that this communication channel is idle chat, which means you likely won't get a response immediately. It could take anything from a couple of seconds to a day, but your message will be seen.
Contributing
Found a bug, got a suggestion, or want to dig into the code base? There are many ways to contribute to the project!
Get started here: Contributing