ArtStation - pre-hard mode Terraria bosses and Terraria Calamity

Steam Workshop::All Alternate Boss, Mini-Boss and Invasion Pack

Official - Behind the scenes of Journey's End - A Q&A with the Programmers and Artists of Terraria, Page 12

ArtStation - pre-hard mode Terraria bosses and Terraria Calamity bosses

Final Pre-Hardmode Checklist! [Terraria - Calamity Mod (72) Master Mode]

ArtStation - Terraria Bosses

Bosses - Calamity Mod Wiki

Official - Behind the scenes of Journey's End - A Q&A with the Programmers and Artists of Terraria, Page 12

The end of pre-hardmode

How To Get Mechanical Skull

ArtStation - King Animation