Clyde is a "bot" integrated into Discord notifying you if you are attempting to do unsupported operations. He reports to you in different scenarios, e.g. changing your nickname, attempting to use server-specific emotes in different guilds or direct messages without Nitro, sending a Message to a user who blocked you, etc. His ID is 1, and his pings (<@1>) only transform into @Clyde if you have summoned his messages at least once in the current session.
Every message sent by it is in the channel or DM Group you attempted to perform that action in and only visible to you. Also the messages can be removed by clicking on the text below it.