Clay Guardian/1.03.24

Temples
Despite having a build time and cost, these Guardians can never be built, but instead are only ever summoned through the use of the Rune and Alchemy spell "Summon Guardian". The Guardians summoned are a defensive structure similar to that of a tower, but without the ability to be garrisoned and will disappear after some time has passed (although pre-placed Guardians on a map wont disappear). This makes them only a temporary solution to plug up holes in your defenses or immediate offensive help, especially for an Alchemist who would normally be fragile and wouldn't otherwise be able to help their army in the midst of a confrontation.

The Clay Guardian is the weakest of them all, and is summoned through the spell only at level 1. They are, at best, a distraction as their offenses are easy to shrug off and their hit points are low. Whether your enemy destroys it or not, it simply wont last long as the Clay Guardian disappears after a few minutes.

Trivia
-Game files indicate that this building costs 100 Stone and has a build time of 30 despite it not being build-able.