Just as you can create your own characters in Mission Architect, you can also create your own custom groups. Custom groups are made up of Minions, Lieutenants and Bosses. Creating your own custom group allows you to populate a mission map with all your own enemies, adding even more control and flexibility to your stories.
You can create a custom group from the My Creations tab in the Mission Browser. Just look for the text that reads My Groups. Select that text then select the button that says Create Custom Group. When you hit this button you'll be taken to another window that will allow you to create or manipulate custom groups. Note, that you can add existing enemies into your custom groups as well.
On the left hand side of this window, you'll notice a large column that displays all your custom enemies. There's also a tab that will let you select any existing enemy in the game. You can select any of these enemies and add them to a new custom group on the right hand side of this window. You do this by selecting the enemy group you want then finding the specific enemy you want to add into your new group. Click on that enemy and you'll see text that reads Add+ next to it. Clicking that enemy again will add it to your new group. If you want to remove a character from a custom group, click on that character in the window on the right. You'll then see an option to remove him.
There are tabs in the enemy group window that will filter the enemies to a specific rank. Clicking Minion, Lieutenant or Boss will show you only the enemies in that group of that rank.
When you select an enemy, you'll notice a preview window on the right will display the enemy and any important information such as name, powers and rank.
Group Level Coverage
At the bottom of the custom group window you'll notice a bar with markings that go from 1 - 50. This bar is a visual representation of the level ranges of your enemy group. It shows you whether or not you have an enemy within that level range. Ideally, you should have multiple minions, lieutenants and bosses in every level range from 1 - 50.
Thankfully, custom characters automatically scale from 1 - 50 so all you have to worry about is having enough variety to keep the group interesting. This is not the case with standard enemies.
Those enemies have a very predefined level range. To that end, when you add existing enemies to your custom groups, make sure you cover your level ranges fully from 1 - 50.