Quick answer
What to do first
Keep a proven wave layout, observe the boss custom attack, and adjust only the coverage layer that breaks first.
The official game description confirms bosses with custom attacks and a relic reward-to-crafting loop. For build a base rng boss waves, first reach the fight with a layout that already handles normal waves. Watch when the custom attack changes the pressure, record whether the entry, middle, or core fails, and change one boss-pressure role before the next attempt. Exact boss health, schedules, thresholds, and required damage are not listed because no current official table was found. After a win, record the relic shown in your session and verify the current crafting panel before spending it.