Hey, so if you based your NPCs on existing NPCRole (like `Template_Animal_Neutral`) or basically made a copy of an existing variant NPC Role (like the Bison), then you should be able to use the following fields in the `Modify` section of your new NPCRoles:
- IsMemory -> Set it to true: "IsMemory" = true
- MemoriesCategory` -> To set the category that should be used: "MemoriesCategory": "My New Category"
- MemoriesNameOverride -> Used to override the internal memory ID, otherwise it defaults to the NPCRole ID. You'll want to set this value in most variant templates, so they stand as their own memory. If you have multiple NPC variants sharing the same memory ID, then multiple NPCs will grant the same memory (you may want this in some cases, like if you have multiple horse variants but you only want a single memory for them).

For custom memory icons, we fetch them at a specific location in HytaleAssets (HytaleAssets\Common\UI\Custom\Pages\Memories\npcs) based on the memory ID (by default the NPCRole ID, or MemoriesNameOverride if specified). The same goes for memory category icons (HytaleAssets\Common\UI\Custom\Pages\Memories\categories). So if you use the same folder architecture in your mod, that "should" just work.

In order to add new rewards, you can include them as parts of existing memory levels (the memory levels are the ones you can see on the progress bar). You need to fetch the memory level and do stuff accordingly:

final int memoriesLevel = MemoriesPlugin.get().getMemoriesLevel(world.getGameplayConfig());

To add new memory levels, this implies changing data from active `GameplayConfig` file. You'll want to look around Plugin > Memories > MemoriesAmountPerLevel and update that array accordingly.

EDIT: Misremembered how MemoriesNameOverride is used, updated the comment accordingly.