Not every Map with mod "contains additional essence" has an Essence

Yeah as the title stated.
Its quite common that the map doesnt have an essence even though you have the modifier contains an additional essence on the map.

I mean you cant miss it, when you complete the map. The essence is a rare mob, so it shouldnt be possible on a map with that mod to complete the map without an essence in your inventory.

Its even more common on maps used on towers.