How do you spawn SI creatures in Cyrodiil using the construction set? I tried making a custom Gatekeeper, gave him a new ID and attempted to add him to the leveled creature lists, but the construction set wouldn't let me. So how can I work around this? Thanks!

In order to add your custom Gatekeeper to a leveled list, you need to make sure the "No low level processing" box is checked. It's just above the Dialogue button to the left of the AI button.

That advice worked! Thank you mate!