It isn't really clear that even the One had time control power. Creating the Orb of Temporance may have involved willingly limiting his own power in that regard.
Different planes have different laws of physics. The gods wrote the laws of physics in their own vault and worked together to write the laws that govern Erebus. There were limitations to what they could write though, such as not being able to control time. When The One removed the power to create ex nihilo, he also removed the ability to rewrite the laws of physics. Such laws can however still be bent somewhat, by anyone with a divine spark. Such rule bending is called magic, but since the rules cannot truly be changed anything magically altered will eventually return to its previous state, even if the one using the magic was a god. Because their divine sparks are closer to the source and so likely stronger, because they have the most experience using magic, and because they know the laws they wrote better than any mortal could hope to learn the gods' magic is far superior to that or men, but their miracles are not eternal.
Ceridwen has access to far more planes of existence than the other gods know exist, and a lot of these were specifically made to have laws radially different from those of Erebus. Connecting planes that operate under different laws of physics allows for the most powerful forms of magic.
Magic also depends upon the raw materials of the 21 precepts. Humans are limited to channeling this from sources in their own plane, or at least planes that are closely connected. Gods do not have this limitation, and neither to Djinni. Each god's own body serves as an immense well of the power of his own precept so they have no need to gather mana together before releasing it. Agares created an infinite plane of each element and created the gems of creation to allow channeling this power out. He made this power available to all the gods, and even the most good gods continue to use his while damning him for the act of making them. Agares hates them mostly for this hypocrisy. The well of power within each god was likely refilled from these gems, although I suspect The One wanted the gods to exhaust their precepts so that they would become balanced and have the true free will that the gods lack. I like to think that The One values freedom as much as Agares, but while Agares thinks he needs power to be free The One knows that no soul can be free unless freed from the burden of power. I think that kind of freedom would be anathema to Ceridwen, who views it as the complete destruction of her precept, so she incited Agares to rebel.
The Gems of Water, Air, and Death have been stolen by mortals, who are now practically as powerful as gods although they remain mortal and don't fully understand how to use the power. In Kael's D&D Campaign, Tuoni, the brother who holds the Gem of Death, was the main enemy behind Tebryn's attempt to destroy the world. He wanted to kill everyone and enslave their souls in order to make a new world of the dead where he would reign supreme. Auric supported the ritual early on but fought to stop it when it came close to completion. When the players stopped it, they allowed Auric to use the power that the ritual had already gathered in order to ascend to be the new god of ice. The brother who held the Gem of Air was not named or encountered, but used as an excuse for why the party could not find any allies willing to help them. He had set himself up as a godking and was trying to conquer the world, or maybe he just loved the thrill of destroying random stuff . All armies sent against him were destroyed by tornadoes. I tend to think that having access to so much of the precepts deeply effected the psyche. The Gem of Air would make its user an extreme daredevil who never thinks of the consequences of his actions, so he would eventually die in an incredible stupid accident. The brother with the Gem of Water seems to have disappeared and never really caused anyone trouble. I suspect the nature of the water sphere meant he became really a passive "go with the flow" type with no interest in ruling the world or hurting anyone. It would make him really introverted and pensive, and perhaps just too lazy to use the gem enough to make him go crazy like his brothers.
getting back on subject...
In the D&D campaign where the forces of Mammon invaded Oghma's vault, that vault was Erebus. I believe that Kael has stated it still happened in FfH canon, although Oghma's vault is not Erebus, the cities of Alexandria and Prespur and the Cliffs of Hastur are in Erebus instead, and Lita the Witch is no longer an angel of Oghma. Mardero was conceived as a half human to get around the Compact, rather than half angel-of-Oghma in order to be immune to the food that wiped the memories of the demons that tried to invade the vault.
It has never been stated that Hastur was involved in the invasion of Oghma's vault, only that armies of Mammon invaded. I conjectured that Hastur is the demon who raped Lita, but that is based mostly on the name of the cliffs from which she was dropped, and in the canon those cliffs are in a part of Erebus now owned by the Balseraphs. As Mammon's archangel he would be the most logical general in that war, but he may not have entered the vault personally. Perhaps he stayed on the outside coordinating strategies, or maybe he foresaw the mist and so just sent demons where they would cause the most damage without any hope that they would remember their orders.
The forces of Mammon invaded Oghma's vault for a specific reason, to find an extremely important secret that could be found only in a library there. The mist means that the demons there don't know what they are seeking though, and wouldn't know if they found it. I have no clue what the secret is, but I tend to think it probably involves The One. Maybe he has secretly returned or found a way to communicate to the Luonnatar. Maybe he left a way to contact him, one secret backdoor into the true heaven. Or it could be something completely different. It is possible that the forces of Mammon recovered some other important secrets before the mist changed the nature of the war. Maybe in Oghma's vault Hastur discovered that he could manipulate the subconscious of a sleeping god to unlock power far greater than that of any waking deity, and could do so without violating the letter of the Compact.
I don't recall Condatis saying how long Hastur has been in her god's vault, but it sounded like it was a relatively recent occurrence. It is possible that she successfully defended the vault of water from the forces of Mammon for several centuries, and has only recently failed to keep Hastur away.
Also of interest, Condatis seems to think that Hastur was coordinating the actions of Tebryn in order to make him destroy the world just to distract her from keeping him away from Danalin. Mammon is not a god who wants the world destroyed, so it seems unlikely that his archangel would risk it unless controlling Danalin is really important.
What if he found evidence in Oghma's vault that controlling Danalin's dreams was the key to defeating The One? What if Oghma planted false evidence to this effect, just to get him to back off or maybe in an attempt to manipulate the master manipulator into doing something that would eventually lead to the downfall of the evil gods?