- Not available on that edition (the reason is in the tooltip)
- Depends on the setting, your class or another addon (details in the tooltip)
What it does
Checks whether your boss mod reports a boss encounter in progress, or the specific encounter whose ID you enter. Leave the encounter ID blank to match any encounter.
Why you might use it
True while your boss mod (DBM or BigWigs, chosen on the Integrations page) reports a boss fight in progress: any encounter, or one boss by its encounter ID. Use it as a switch condition for an encounter-specific rotation, or to save cooldowns for bosses instead of trash. It follows the boss mod rather than the game, starting when the boss mod engages and ending on a win, wipe or reset, and it is unavailable when no boss mod is enabled or loaded. It is offered on Classic Era, TBC Anniversary and Classic progression, not on Retail or WoW Forever.
Example
your boss mod reports an encounter in progress
Settings
What each setting in the condition editor means, from the game's own help.
True while your enabled boss mod (DBM or BigWigs, chosen on the Integrations page) reports a boss encounter in progress. Leave Encounter ID blank for any encounter, or enter the game's encounter ID, which DBM and BigWigs share, to match one boss; while an encounter is active the editor shows its name and ID. This is the boss mod's report, not game state: it starts when the boss mod engages and ends when it records a win, wipe or reset. Use it as a switch condition for encounter-specific rotations; automatic switching picks it up on its normal re-check interval. Unavailable, never simply false, when no boss mod is enabled or loaded.