The site owner captured these two enemy building cards in our demo run (v0.19.4e). They describe effects without giving numeric stats.

Imperial Fortress

A dark, spiked tower with orange firelight inside its gate. The card reads:

IMPERIAL FORTRESS

Protected by hordes of enemies who will break out when the fortress falls

Imperial Fortress card showing a dark spiked tower and the fortress-falls description.
Enemy card from our demo run (v0.19.4e).

The stated trigger is the fortress falling. Which enemies break out is unknown. The card does not mention a boss; a boss trigger from reaching the gate is unverified. It does not establish that staying away delays a boss. See the Troll Rider checklist.

Corrupted Shrine

A dark standing stone with a glowing red band, red gem and red runes. The card reads:

CORRUPTED SHRINE

Empowers the marching hordes with cold discipline, increasing their overall strength

Corrupted Shrine card showing a red-rune standing stone and its marching-hordes description.
Enemy card from our demo run (v0.19.4e).

The shrine's range, numeric values, duration and whether it can be destroyed are unknown. A connection to stronger versions of the same enemy rank is unconfirmed. These cards do not identify an Elite variant or establish whether a boss is involved (unconfirmed).