D&D 5th: Demon Tower of Madness
A very old deity, Helm is the eternal sentry and is always represented as a god and seen wearing a full suit of armor that represents the weight of his heavy responsibility to his task. Yet it is clear that Helm gets, and has always gotten, the job at hand done without there being any complaint made. The people of the Realms widely admired these qualities in what they saw as a humble and reassuring god of the pantheon.
During the Time of Troubles, however, when the gods walked among Toril, it was in the reliable Helm that Lord Ao trusted the task of keeping the other deities from returning to their posts without returning the stolen Tablets of Fate. Helm kept his full power for this task, so that when the goddess of magic, Mystra, attempted to pass him on the stair without the Tablets he was capable of first blocking her and after, when she retaliated, destroying her completely. This action had enormous repercussions for Helm, and while it put off any of the other earthbound deities attempting the same action, it also caused the other deities and mortals alike to hold Helm in great contempt (surprisingly however, in the South, Helm’s following was still quite strong among mortal beings).
When the Time of Troubles ended and (what was left of) the other gods were restored to their former existences, and Helm himself no longer bound to stand guard against them, much of Helm’s worship had faltered. Things amongst his clergy were made worse when the natives of recently discovered Maztica, whom the priests of Helm were subjugating in their conquest of the region, highlighted their cause. It is only in recent times that Helm has regained some of his popularity and respect, as people acknowledge that in the Time of Troubles he was doing what he had to. The only god who could be considered a full ally of the Watcher is Torm the True, the god of paladins. Strongly held ideological differences have caused a great rivalry verging on hatred between the clergy of the two gods, but the deities themselves remain close.
Far back in time, the deity Lathander caused a divine purge known as the Dawn Cataclysm in which Helm’s lover, a lesser deity of pragmatism called Murdane, was victim. Helm has begrudged the Morninglord this ever since. However Helm reserves his real opposition for deities whose plots threaten the people and stability of Faerûn, especially Bane and Cyric, as well as Mask and Shar. He is also especially at odds with the uncontrolled violence and careless destruction of the deities Garagos, Malar and Talos.
According to The Grand History of the Realms, Helm is eventually killed by Tyr in 1384 DR, though the other gods suspect Cyric is somehow behind it.