Boss Rush - Official Calamity Mod Wiki

The Boss Rush is a special event that is activated upon the use of Terminus. Although it can be summoned at any point in the game, it is recommended to be fought after all other bosses are defeated. During the event, every vanilla and Calamity boss spawns sequentially in a predetermined order. The bosses summoned have immensely buffed HP and damage and use modified AI, giving them all similar difficulties despite their usual distance in the game's progression. The Boss Rush can be deactivated at any time by using Terminus again.

Bosses - Official Calamity Mod Wiki

Yharon, Dragon of Rebirth - Official Calamity Mod Wiki

Cryogen - Calamity Mod Wiki

Boss Rush - Calamity Mod Wiki

Boss Rush - Calamity Mod Wiki

The ultimate boss rush : r/CalamityMod

I did it! I finally beat the boss rush while tripping balls! : r/CalamityMod

Calamity Mod All Bosses and Minibosses in a Nutshell

The Twins - Official Calamity Mod Wiki