When I put a * in the "Event Initiated by" box (see image), it wont let me save and throws an error.
You don't need to put a *
Just leave the field empty and it should take a value of "any" once you're done.
I am trying to create a custom Azure Alert that sends an email whenever "A SQL Database is created by anyone" in any resource group across my subscription.
I see a difference between the wording here and the rule you're trying to configure as per the image in your question. I say this because in the image you seem to select "testserver/testdb" as target under a particular Resource group "SQL-Sandbox".
This configuration will not be equivalent to monitoring across your subscription.
If you want to monitor across your subscription, you can configure your target in 2 possible ways. I quickly tried this out as well in a free subscription and will show screenshots.
Target is simply the top level subscription and nothing else.
Target is All databases under the top level subscription.
