The Onboarding Cycles Custom Object allows you to track information about the post-sales process in Salesforce.
If you are using this Custom Object, the Validation Rule, "Require Fields on the Onboarding Object for Stage Changes" enforces reps to capture required fields at a particular Onboarding Stage.
For example, if you have a Onboarding record on the Stage "Requirements Gathering," you can enforce that reps enter in the following fields:
Go Live Date
Kick Off Date
Opportunity
Furthermore, you can personalize the Validation Error Message as such "For Stage, "Requirements Gathering," please enter the Kickoff Date, Go Live Date, and link the Opportunity tied to Onboarding."
Using the above example, your variable inputs will be as such: