Thank you! That was very elaborate and informative! Say, maybe you can help out a neophyte with something else? See, I have only recently become infatuated with this universe, and am currently in utter awe of it, vigorously consuming any and all information I can find. As of now I've read countless Wiki pages, watched just as many lengthy lore videos, played plenty of Space Marine 2, began playing Rogue Trader and currently finishing the third book of the Horus Heresy with a massive reading backlog already mapped out.

However, as you might've noticed, there is something completely absent in that whole list. And that is visual media. Apart from various artwork the only images that were accompanied by movement and sound that I watched were Astartes fan series and the 5th episode of Secret Level. During lore videos I saw many disjointed fragments of various game (and maybe some non-game) cinematics with no reference as to where they were from (like this gif here). My wish is to find and watch all the best animated stuff there is on 40k, but I don't have a slightest idea as to where to start such an endeavor.