Steven Universe: Diamond Days starts today. Here are my predictions of what will happen in that special event.
White Diamond will remove Steven’s gem, bringing Pink Diamond back.
In “Three Gems and a Baby“, Pearl grabbed Baby Steven’s gem with the intention of removing it from his body to be with Rose Quartz again but decided against it. Pearl is a white Gem with her gem in her forehead like White Diamond and Steven’s gem is later revealed to be actually the gem of Pink Diamond.
Steven’s gem being removed will increase his strength and then give him a transformation that increases his power.
In “Garnet’s Universe”, Garnet removes her hair to increase her power in a bid to defeat Ultimate Ringo. After Ultimate Ringo turns her photo into an onion ring and eats it, she is riled and gains a pink transformation with large pink hair and finally defeats him.
Steven’s gem being removed could actually increase his power if it turns out that it held back his true power and his abilities are actually ingrained into him. Still without his gem, after Steven is riled, he gains a pink transformation that makes him look like Rose Quartz, Pink Diamond or both with pink hair. In “Storm in the Room“, Steven told Rose that he thought about dying his hair pink more than once.
The reason why the Sun Incinerator means so much to Emerald will be revealed.
It was stated that Emerald is a major Season 5 antagonist that will return so she’s going to be a part of Diamond Days.
Ships and their Gem owners are shades of a colour shared between them; we’ve seen this with Aquamarine and her ship and Emerald and her Destiny Destroyer. The Sun Incinerator is a Gem ship that is shades of yellow, brown and dark green. A Heliodor, a beryl like Emerald that is yellow, could’ve been the original owner of the Sun Incinerator. Heliodor means “gift of the sun” in Greek and the Sun Incinerator’s hull is shaped like a hexagonal prism, a possible reference to Heliodor [and the rest of the beryls] belonging to the hexagonal crystal system.
Potentially, Emerald and Heliodor were close friends and the former gained ownership of the Sun Incinerator as a keepsake after the latter was shattered in The Rebellion. That would explain why Emerald had the Sun Incinerator guarded by 67 elite Citrines and looked mournful when she told Lars that stealing it was “unacceptable”.
It will turn out that Heliodor is alive and that she faked her death.
At the end of "Mindful Education", we see a little yellow bird that pecks the ground three times before flying away. The bird's inclusion seemed a little superfluous; if it never appeared, no difference would've been made. What if, the bird is actually a Gem in disguise like how Pink Diamond disguised herself as Rose Quartz. The bird's gem wasn't visible because it was most likely positioned right inside her body.
The bird's true form is Heliodor, who faked her death to stay on Earth just like Pink Diamond did. Heliodor's reason for faking her death to stay on Earth could be because she was blackmailed into shattering Crystal Gems during the Rebellion after she refused due to not wanting to shatter other gems. Her mentality mirrors that of Steven's in "Ocean Gem", in which he said "Gems shouldn't fight each other" and "We Gems should be friends". Heliodor shape-shifted into a bird to keep a low profile on Earth.
During Diamond Days, Lars and the Off Colors return to Homeworld in the Sun Incinerator to come to Steven's aid. Emerald shows up to attack Lars and the Off Colors as retribution for them stealing her Sun Incinerator. Emerald says out loud, "This is for you, Heliodor." Steven, for whatever reason, returns to Earth using Lars' hair and just as he is about to return to Homeworld through Lion's mane, Steven says to himself what Emerald said and asks himself what she meant by Heliodor.
Heliodor, in her bird form, overheard Steven and follows him into Lion's mane and back to Homeworld. Heliodor sees Emerald and reverts to her true form. An ecstatic and emotional Emerald runs to Heliodor and hugs her before the latter explains what actually happened to her during the Rebellion.
Heliodor would most likely become a Crystal Gem because like them, she is pacifistic and only fights when all other peaceful options have been exhausted.
Ruby will die.
Cat Steven’s left eye is blue like Garnet’s left eye. Cat Steven missing their right eye could be foreshadowing our Ruby’s death.
Garnet’s red right eye is representative of Ruby. In “Keeping It Together”, Garnet said she’d “always exist in” Ruby and Sapphire, even if she splits apart. To me, that seems like foreshadowing towards Garnet no longer being able to exist on a physical plane if Ruby or Sapphire is killed.
This next piece of evidence was pointed out to me by speculation of Ruby’s death I read on one of Steven Universe’s TV Tropes WMG (Wild Mass Guessing) pages in the past. The top-most right hand of the Gem fusion statue of the Crystal Temple is raised with a Warp Pad on it. That hand can be representative of Sapphire’s gem placement. The top-most left arm of the statue is missing its hand and Ruby’s gem is in the palm of her left hand.
