Bestiary is per world:
Bestiary progress is tied to a world, not a character (source).
And I was thinking about crimson and corruption creatures, where I can create new world, get missing in my world blocks and just bring them into mine. It should work in theory (confirm?).
But what about other cases? Killing Skeletron before Dungeon Defender? What else?
Is it always possible? Or should I be careful with something?
02 Answers
You can always complete the Bestiary, but you will also need enemies from the other type of evil. This includes the evil-specific bosses, the Eater of Worlds and the Brain of Cthulhu.
You can accomplish this by taking some Ebonstone or Crimstone from a different world, or by purchasing the appropriate seeds from the Dryad. Once in hardmode, the Dryad will sell seeds for the evil that is not native to your world if she's in a graveyard biome, created by placing six or more tombstones close to each other.
Some NPCs and enemies require the ingame Halloween or Christmas events in order to spawn, which are normally only available in accordance to your system's clock. It is possible, however, to trigger a single ingame day of Halloween or Christmas by defeating the Pumpkin Moon or the Frost Moon respectively.
The entries for the only two missable enemies, the Dungeon Guardian and the Tortured Soul, can be obtained by talking to the Clothier and Tax Collector NPCs respectively. Every other enemy that was missable prior to 1.4 (due to being exclusive to worlds pre-hardmode) can now be found in hard mode as well.
4It depends on the world. If your world is an old world prior to 1.3, and underground desert biome is not generated, and therefore you are not able to find those creatures. You are unable to create artificial Underground desert biome, but again, you can use TEdit to modify your world and add that biome to finish up the bestiary.
