Part five of a series on building Babel, an open-source chat widget and API with PubNub, focuses on creating a self-destructing chatroom UI on top of a previously developed self-destructing messaging system. The post details how to implement explode.js for message destruction, set up an HTML structure for the chat UI, and add custom countdowns for messages using jQuery and JavaScript methods such as setInterval for countdowns and explode.js for a dynamic destruction effect. It emphasizes the need to sign up for a PubNub account to acquire unique keys and utilize the PubNub JavaScript SDK for initializing and managing the chatroom's functionalities. The series aims to enhance user experience by offering encrypted, self-destructing messaging with public key exchanges, providing a live demonstration and access to the source code on GitHub for further exploration and application.