Event Message customization under Event Policy.

@Abhishek_Garg Besides the inclusion of static message text defined in the event policy, the generated event message is driven by the contents of the source alert; this applies to the use of Regular Expressions in this field as well as to each of the available variables (%M, %I, %V, %T) [Source: The Event Message Tab]. 

In other words, concerning the generated event message itself unless this data is in the source alert it is not accessible to be included in the event message. You've not stated though how these alerts are being generated, but I will highlight that events must be associated with an SL1 entity. If resulting events are aligned to a device component, the relationship to ancestors will be visible within SL1 from the viewpoint of the device (ex. Device Investigator). Such ancestor information is also accessible to Run Book Automations that may be triggered from such an event using such variables as %X for the entity's name to which the event is aligned or %_root_name for the associated root device's name: Run Book Variables