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Some overlap with Mr. Exposition as well.
Not quite the mysterious informant. Character is known to the others, works in the same organization but with more knowledge and works directly but secretly for the higher power. Maybe just a little of Mr. Exposition (temporarily, it never stays with one character permanently). Part of the infodump is that the character works directly for the higher power.
Character who is working for a higher power, are currently aligned but not always exactly the same goals as the main protagonists, provides new information to other characters, confirms hinted at information to readers.