Quick answer
Direct official-warning answer, explicit unknown behavior/timing/tactic state, and a reproducible encounter observation checklist.
Start here when this is the exact player task you searched for. The sections below turn the question into steps, checks, and next pages.
Searching for “Flatten The Mountain eagle” or “how to avoid the eagle Flatten The Mountain”? The official description warns about the eagle, but no repeatable trigger, timing, behavior, or avoidance tactic was confirmed. This direct checked answer says the eagle is an official warning, behavior, timing, and tactics are not confirmed, and the observation checklist separates player reports from confirmed mechanics.