1.18 Raid Changes

Why are so many raid farms broken in 1.18?

All mobs spawned by raids are raider entities. Raider entities that are participating in an active raid will look for raider entities that aren't in a raid that are within a 32 block cube, and try to recruit them.

In 1.17 and below, raiders would recruit mobs every 20 ticks, based on their age. This means that the raiders would try to recruit in the tick they are spawned, again 20 ticks after they are spawned, then 40, and so on.

In a 1.18 snapshot, this was changed so that half of the raiders would try to recruit one tick later. This means that half the raiders would try to recruit one tick after they are spawned, 21 ticks after they are spawned, then 41, and so on.

Now, since 1.18 pre 8, this has been changed again. The current way that raiders choose when to recruit is similar to the first, but this time it is every 21 ticks instead of every 20, and starting one tick later. Raiders will try to recruit one tick after they are spawned, 22 ticks after they are spawned, 43 ticks after they are spawned, and so on.


Why does this change break raid farms?

The change has to do with getting bad omen. Only mobs that are not included in an active raid can give bad omen, and the mechanics related to mobs joining and leaving raids were altered.

In 1.17 and below, recruitment didn't have very much effect. There are a lot of reasons for this, but the main one has to do with the 16 block limit on recruitment. Raiders can't be recruited for the first 20 ticks of their lifetime because they are already part of a raid. What this means is that if the raiders fall 16 blocks in their first 20 ticks of life, then they can't be recruited by the raiders trying to recruit right when they spawn. In most raid farms, raiders would be removed from the raid that spawned them before they ever try to recruit for a second time. However, every 20 ticks in world time (independent of any raid events), all raiders will look for a nearby raid to join. To use CCS_Covenant's farm as an example: When the raiders join nearby raids every 20 ticks, the only raids they can join are ones which have just spawned and haven't been shifted yet. This already means that it's not very likely that a raid will be present when the mobs try to join, but the reason this never had any effect on rates is that it was almost impossible for the 20 tick joining mechanic to cause both player attacks to fail, only one. This is because of how raider removal is timed. If the other one still was successful, then the next raid would still start. When raider entities joined a raid, all the entities would leave it at the same time 20 ticks later, meaning they could give bad omen to the player.

The 1.18 pre 8 mechanic is much harder to deal with. What causes the steep decline in rates is because raiders now have two ticks during which they can join a raid before they try to recruit other raiders at 22 ticks after spawn. Therefore, its much more common for the recruitment mechanic to actually be used, so raider entities are more likely to be part of a raid when killed by the player. But I said before that it's unlikely that there will be a raid present at all when raider entities try to join every 20 ticks. While this is the case, the recruitment mechanic can cause a chain reaction that takes a long time to dissapate, having a large impact on farm rates.


What can you do about it?

While there are no outright fixes for this change, there are some useful workarounds. The most reliable workaround is to make sure there is an occupied POI in a 3x3x3 subchunk region around the raid mobs. Having a nearby POI will make sure the raiders never use the recruitment mechanic. The drawback to this workaround is that it makes it much harder to stack raids, increasing design effort and build effort for raid farms. The next workaround is not as reliable, but it can work in many situations. Giving the raiders a direct line of sight to a villager or golem will make them target that mob. While they are targeting a mob, they also don't try to recruit other raider entities. The last and most useful workaround (at least for designing new farms) is to time the raid starting so that whenever raiders are looking to join a raid, there isn't one to join. For example, 10 tick or 20 tick raid farms don't have this problem if they are synced properly with the world clock.

Explanation by Real_NC, or Nick (NDD)#9738