So I definitely think the "Apothicon Servant Upgrade" should be accessible now. The reason being is in the Patch Notes, when pertaining to Shadows it simply says something about, "an Easter Egg being fixed".
Now the difference is when pertaining to Der Eisendrache, it specifically states, "fixed an issue around the Main Easter Egg".
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So a specific "Easter Egg" within Shadows has been fixed, but nothing is ever said about the "Main Easter Egg". This leads me to believe, Treyarch has finally fixed whatever problem there was involved with not being able to achieve this.
I have a Theory the reason we could "Glitch the Margwa" was in fact due to the "Apothicon Servant Upgrade Quest" being broken. Since you had to build it before placing the Final Gateworm and opening PaP, it makes sense this is the case.
See in the Patch Notes it was also stated that "an error was resolved for a player to begin an Easter Egg when obtaining a Specific Gun". In the case of glitching the Margwa, you had to obtain a specific gun, before placing the Final gateworm, leading to the Margwa no longer spawning, and the Shadow Man getting stuck.
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Also remember we have the "Noire Easter Egg" this is where we get the Black & White filter on the Screen. Well we've never been able to find the end to this specific Easter Egg, when in the coding it's clear theirs definitely a way to end or complete it.
I really think this may actually be how we obtain a "Cocoon". As the player the Map changes and is in Black & White, but once we Transform into the "Beast" the Map changes and turns to Color.
This reminds me a lot of MotD, where we would go into afterlife and could see the Crystal Skulls, but once we turned back into the player we could no longer see them. We just knew of the location where we could throw the Tomahawk. This Easter Egg also led to the "Hidden Blundergat" in the Wardens Office.
So maybe Once in this "Noire Mode" when we Transform into the "Beast" we can find the "Cocoon" and possibly Grapple it. Which is basically the same thing as throwing the Tomahawk to obtain the Crystal Skulls in MotD.
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Food for thought nonetheless!
*The "Cocoons" not Spawning in, possibly to do with the "Noire Mode" being there's a way to end it, but we've yet to figure it out.
*This is what I was talking about, when building the "Apothicon Servant" before placing the Gateworms, as that's rare and not a lot of people are going to do this outside of Solo.
*This probably pertains to the Gateworm not Spawning. Since it states "Shadows of Evil Easter Egg"
*Notice the difference where it says Main Easter Egg when talking about the Main Quest.