Timed Aggression was a mechanic added in Revengeance, Death, and Malice Mode. It caused bosses to enter later phases based on time elapsed during battle in addition to their current health. As a result, bosses could enter later phases prior to reaching the health threshold if the player had fought the boss for long enough.
Timed Aggression passively activated on all bosses in vanilla Terraria and the Calamity Mod, which have an assigned value indicating a rough estimate of how long each boss takes to defeat using average on-tier equipment outside of the Boss Rush, timed from when the boss spawns. A phase change occurred when the time elapsed had exceed 1.5 times of the product of the health ratio and expected kill time.
For example, King Slime has an expected kill time of 60 seconds, and summons the Crown Jewel at 50% of its health in Revengeance Mode. As a result of Timed Aggression, it would summon Crown Jewel regardless of its health after 45 seconds have passed, as calculated by the following: 1.5 * 0.50 * 60 = 45
Kill Time Table
The following includes the kill time values for each boss. Several bosses have multiple values for different phases.
Boss |
Kill Time (seconds)
|
King Slime |
60
|
Desert Scourge |
60
|
Eye of Cthulhu |
90
|
Crabulon |
90
|
Eater of Worlds |
120
|
Brain of Cthulhu (Creepers) |
30
|
Brain of Cthulhu |
90
|
The Hive Mind |
120
|
The Perforator Hive |
120
|
Queen Bee |
120
|
Skeletron |
120
|
The Slime God (Slimes) |
90
|
The Slime God (Core) |
180
|
Wall of Flesh |
120
|
Cryogen |
180
|
The Twins |
180
|
Brimstone Elemental |
180
|
The Destroyer |
180
|
Aquatic Scourge |
120
|
Skeletron Prime |
180
|
Calamitas Clone |
240
|
Plantera |
180
|
Leviathan and Anahita |
180
|
Astrum Aureus |
180
|
Golem |
150
|
The Plaguebringer Goliath |
180
|
Duke Fishron |
150
|
Ravager |
180
|
Lunatic Cultist |
150
|
Astrum Deus (Phase 1) |
60
|
Astrum Deus (Phase 2) |
120
|
Moon Lord (Head & Hands) |
120
|
Moon Lord (Core) |
240
|
Profaned Guardians |
90
|
Dragonfolly |
120
|
Providence, the Profaned Goddess |
240
|
Ceaseless Void (Dark Energies) |
20
|
Ceaseless Void |
180
|
Storm Weaver |
135
|
Signus, Envoy of the Devourer |
120
|
Polterghast |
180
|
The Old Duke |
180
|
The Devourer of Gods (Phase 2) |
240
|
Yharon, Dragon of Rebirth |
255
|
Exo Mechs |
360
|
Supreme Witch, Calamitas |
300
|
Adult Eidolon Wyrm |
300
|