Discussion of third-tier monsters.

Well, the poll features creatures from castles, from the actual buildings. Elementals, however, are all recruited from the portal.
In general, elementals are not really a 3rd-level unit, perhaps only formally. Their stats are low for their level, but on the other hand, they are too high for the 2nd level, so they were kind of crammed into the 3rd level. Their place in the classification actually reflects the magic of Nature well: elementals are summoned on the third level of the school, the 2nd level on the 2nd, and the rest of the 3rd level on the 4th level of the school.