Until Cryogen is defeated, you will only have access to the vanilla hardmode armours. Daedalus Armour (Obtainable after Cryonic ore spawns from defeating Cryogen.Serves as the final Pre-Hardmode armour.) Crafted from the Purified Gel dropped by Slime God. Statigel Armour (Obtainable after deafeating Slime God.Aerospec Armour (Obtainable after defeating the Hive Mind or Perforators which causes the ore to spawn in your world.).All of these are dropped by the Cnidrion and Desert Scourge.) Bars are crafted using Seashells, Starfish and Coral along with Victory Shards. Victide Armour (Obtainable from the moment you spawn in, although it’s incredibly grindy.Shards used in crafting are dropped by Wulfrum Slimes and Wulfrum Drones on the surface.) Wulfrum Armour (Obtainable from the moment you spawn in.

You obtain various armours throughout the game. Mod is considered complete after Yharon is defeated)

Supreme Calamitas (Optional Superboss.

Polterghast (Can be done before Sentinels).Sentinels of the Devourer (Order of the Sentinels doesn’t matter).

Ravager (Drops cores which are useful but otherwise has no drops of value and can be skipped).

Plaguebringer Goliath (Drops little of value for melee, mage and summoner builds and can be skipped).

Brimstone Elemental (Drops little of value for non-melee builds until Providence is dead and can be skipped until then).

While the bosses in each segment of the game can be beaten in any order, I suggest following an order similar to what is suggested by Boss Checklist and the Calamity Mod wiki. The bosses in the mod are the core of progression.

How to survive in the abyss calamity