Arena is asynchronous: publish your boss for other players to challenge, then attack published opponents on your schedule. Attachment levels are normalized, while parts, synergies and Brain mechanics remain part of the matchup.
Publish a machine with a clear plan
You build one boss from your collection and use it across the game. Publishing makes a build available for asynchronous challenges, so the opponent does not need to be online when you attack.
Check that the published machine is the version you intend others to face. A coherent range plan, usable mobility and sensible Brain behavior matter because the machine must function as an opponent as well as in your own hands.
Understand what normalization changes
Arena strips attachment-level advantages. It does not erase collection differences or make every loadout identical: weapon type, body, mobility, support effects, synergies and Brain rules remain.
This is why a successful leveled Campaign build may need revision in Arena. A part that survived through extra attachment health in Campaign can become a different durability tradeoff after normalization. Test the mechanics rather than assuming the same outcome.
Read opponents and defense results
Arena includes published players and explicitly labeled lab rivals. Keep that distinction in mind when interpreting a result. Use the defense log and Revenge options as opportunities to inspect which build interactions caused trouble.
At timeout, Arena compares remaining core-health fractions, unlike Campaign’s required knockout. A result still depends on the full exchange, including control timing. Use rewards and rating as feedback, but look at range, resource uptime and module survival to decide what to change in the Workshop.