Arknights resources
Arknights is a mobile tower defense gacha game originally released in China and available in English worldwide. The English server is 6 months behind the Chinese one.
The game is known to be very story heavy, and often covers themes of international politics and socioeconomic oppression. As a strategy game it's dynamic and varied, with many different gamemodes approaching its core gameplay from different angles, and units offering many different ways to engage with the game systems.
Arknights Toolbox
Automatically datamines gameplay information and presents it in a fast-loading interface.
Oldwell
Keeps track of the events and banners that happened in the space between Global and CN versions to help plan ahead.
Penguin Statistics
Crowdsourced material drop statistics.
Tomimi.dev
Lets you filter operators by their gameplay functionality, and also calculates stats for enemies in the roguelike modes.
PRTS.map
Detailed information on enemy pathing for every map.
/akg/ Resources
Primarily used for the story reader, which datamine archives all the game's story scripts and formats them with sprites for easy reading.
Arkrec
A community-run archive of challenge clears, aiming for the least amount of operators used within each given restriction.
Lungmen Dragons
The western community for Arknights challenge runs.
Arknights Terra Wiki
The English wiki. In general I do not recommend it whatsoever for story information, and I personally also dislike the way they present gameplay information. However, they're very useful when it comes to information on the game's music.
PRTS.wiki
The Chinese wiki, much more extensive and rigorously maintained than the English one. My favourite page of theirs is the list of every scene that each operator appears in.
Monster Siren Records
The official website for Arknights' fictional music label, listing all the ingame OST as well as character EP's.