You can reward based on an object a record is related to. E.g If your chosen object is an Event or Task choose to only generate a reward if the 'Task is related to an Account' record
The Criteria field selection will include Name ID (What Id) and Related To ID (Who Id) if relevant on the selected Object
The Related to option needs to be selected from the Condition picklist then the Field picklist will display a list of the related Objects available
Tip: Behaviour Nudges will then also be displayed on the related object's records, as well as on the 'Task or Event' record
Rewarding Specific Related Object's Record
It's also possible to reward based on a single related Object's record, e.g generate a reward if the 'Task is related to a specific Account' - in this example, Acme
Instead of selecting Related to for the Condition, select equals, select the Object from the picklist and type the Exact name of the required Account: