Found under Setup > Support > Escalation Rules, ticket escalation rules allow you to specify actions to take automatically if a support ticket has been in a specified state for a set period of time.
You can select the Departments, Statuses and Priorities that the escalation rule applies to. For example, in the picture below, low and medium priority tickets will be changed to high, a response will be automatically made to the client and an email sent to the members of the specific support department after 4 hours with no response:
Escalations are checked by running a cron file with parameters:
php -q \path\to\home\public_html\whmcspath\admin\cron.php escalations
Please note the space between cron.php and escalations. The command will run the escalations section of the cron file only.
Escalation rules only apply to tickets submitted after the escalation rule. Tickets submitted before will not be escalated automatically.