Necropolis – “Dawn from All Sides” [Campaign 2, Mission 3]

But Lamassu are found in the Dungeon. You can recruit and build them (build and recruit) right after completing the additional quest... Although, I haven't seen much point in them yet.

I went to the Dungeon almost at the very end, when enough time had passed. As a result, I gained a lot of experience there in battles, and even with auto-battles, there were no losses.

In the beginning, Orcs are easily defeated by dark elements. Moreover, it's better not to use the elements directly: just summon them behind the enemy and have them defend. Thanks to this, they receive -50% damage due to the general elemental ability. Then you can cast "Drain" on them, and the Orc will no longer be able to kill them.