The Summoner
I don't know of any real easter eggs here yet, but this level has enough interesting things without them.
Look around where your units first beam in. There is a device with three pits, and a big field of "void".
Those devices are used to deactivate two barriers in this level - were those voids once barriers, before the Tain shattered?
There are a total of seven of these devices, two gates and five voids. But if the voids were once gates, where did that one pit of void in the middle lead? 5D space?
If you look very closely at the tiny "crystals" you must position near the devices to deactivate the gates, you will see that they are themselves tiny Tains! This is also true of the crystals elsewhere in the games and of Shiver's projectiles.
Near the end, there is a passageway guarded by four Tain towers, which can only be passed by having the Deceiver (or presumably any mage) pick up a magic crystal and stand in the passage. The towers will strike him, and cause no collateral damage to other units passing.
And in the final section, we see a Myrkridian skull platform, minus the standard. Was this the same one the Legionairres passed in TFL?
Addendum: If you look even further past the skull platform in the final section of the map, you can see a Tain exit-arch, just like from The Smiths of Muirthemne level in TFL. Maybe this IS where the narrator passed by back then...
Written and compiled by Forrest.