The phrase "under/in the guise of" can be replaced with a number of synonyms, each with slightly different connotations. These synonyms include "pretending to be", "masquerading as", "posing as", "disguising oneself as", "assuming the identity of", and "passing oneself off as". All of these phrases imply that someone is taking on an identity or role that is not their own, often to deceive or mislead others. Whether it is a spy who is "posing as" a civilian, a criminal who is "masquerading as" a law-abiding citizen, or a politician who is "passing themselves off as" an expert on a topic they know little about, the phrase "under/in the guise of" captures the sense of false pretenses and hidden motives.