The Sheeda inhabit the Earth 1 billion years in the future.
They are either the genetically engineered or evolved descendants of humanity, or they are the descendants of some race who comes after humanity. They are somehow related to both spiders and scorpions and possess 'crests', which give them access to animalistic powers.
The Sheeda had realized that they were the last race who would ever inhabit the Earth, and the culture had devolved to callous survival as a result of this realization. However, all this changed with the arrival of an automated time-machine built by advanced Neanderthals, which arrived in their domain one day. Reverse-engineering the device, the Sheeda returned to Neanderthal times and promptly raided the Earth. Realizing that they could prolong their empire's rule by plundering the Earth's past, the Sheeda reorganized the civilization to take advantage of regular 'harvesting' operations.
During the attack on the Camelot, capital of the Commonwealth of Avalon in 80000 BC, King Melmoth of the Sheeda was deposed by his wife, who assumed the title Gloriana Tenebrae. It is under her rule that preparations were made to attack present-day America, as part of an agreement with the Darkseid of that era, starting with New York.
As part of preparation, Gloriana Tenebrae organized attacks on the Newsboys of Nowhere Street, the Ultramarine Corps, the JLA, and the Seven Soldiers of Victory. This was due to a prophecy that "seven soldiers" would depose her. Another part of preparations was her efforts to reclaim the Seven Imperishable Treasures; seven gifts given to the Neanderthals by the New Gods, stolen by Melmoth, stolen from Melmoth by King Arthur at the height of his reign and ultimately lost in the fall of Camelot. By the beginning of the invasion, they had reclaimed the sword Caliburn Ex Calibur and the Cauldron of Unwhen.
However, the invasion hit a number of problems as it arrived. The first was the destruction of the majority of its ships in a terrorist assault by Frankenstein. When the sole remaining ship arrived, it was opposed by the people of New York, led by the Manhattan Guardian, whose mentor, the last member of the Newsboys of Nowhere Street, had warned him about the Sheeda. This force was later joined by a tribe of intelligent superpowered horses, descended from one of the Seven Imperishable Treasures.
While the invasion force was thus stymied, Gloriana was attacked by Ystina the Shining Knight, time-lost last survivor of Camelot, and then by I Spyder, the last survivor of the Seven Soldiers of Victory (who had been masquerading as her servant all along.) Thrown from the balcony of her flagship, she was accidentally killed in a car crash, by a vehicle driven by the Bulleteer. Meanwhile, her ship was commandeered by Klarion the Witch Boy, who piloted it back to the far future, where he appears to have taken control of the Sheeda.
Since the Sheeda only become active either while invading another time-zone or while preparing to invade another time-zone, it is unlikely they will be seen again in present-day continuity.
In the Zatanna portion of the crossover, it was revealed that the Sheeda owed their existence to a being named Zor, a renegade Time Tailor, who rewrote reality so that they would attack the present day. When during the crossover Zor was captured by Zatanna and his fellow Time Tailors, it is unknown whether the Sheeda can continue in their present form.
In addition, editorial comments by Dan Didio and Grant Morrison have pointed out that the story's proximity to the events of Infinite Crisis puts certain story elements under strain. For example, several characters who debuted in Seven Soldiers appeared in Infinite Crisis, but portions of the story, such as the New Gods living in secret as homeless New Yorkers, were proved false by several post-Infinite Crisis stories.
The Sheeda are connected to several characters who are still extant in continuity:
- Misty Kilgore, the daughter of Melmoth, last seen as Zatanna's apprentice.
- Klarion the Witch Boy, descended from Melmoth, still active in the modern DCU.
- In addition, several heroes, such as Frankenstein, Bulleteer, and the current Shining Knight, owe their origins to the Sheeda's actions.
Level of Technology:
Extremely High. The Sheeda seemed to possess technology they had inherited/stolen from various factions of the DCU. Among them were Erdel Gates for teleportation to Mars, Green Lantern Power Batteries called 'Truth Lanterns' which could create constructs for the Sheeda, and what appeared to be versions of Chemo to do their fighting when it suited them. They also possessed considerable Fourth World tech that they had plundered from the Neanderthal Age they had Harrowed.
- The use of the dating "1 billion years in the future" comes from Frankenstein #4, which was printed in late 2005. Given the tone of the comic, it may not be exactly accurate, however, it is used simply because it is the only date we have been given, or are ever likely to be given.
- The Sheeda are superficially similar to fairies, but whether there is any connection between the two is unknown.
- Much of this information is taken from the Wikipedia entry on the Sheeda, here.