Official rule text
1.5 If an ability contains the word “Action,” a player must use a same time during the action phase, each player takes a turn component action during the action phase to resolve that ability. resolving an ability in initiative order, beginning with the active player. This process continues until each player has resolved
View official source
Source: Twilight Imperium: Fourth Edition - Living Rules Reference: Prophecy of Kings
Expansion: Prophecy of Kings
Version: 2.0
Reference: Rule 1.5