Eternium - Stop the Ritual - Act 3 Q1, where is it on the map?

Given you mean the optional daily quest (blue) by Liana, which leads you to the first chapter "The rusty planet" of Act 3 "Divine Pyramids" (manually translated) I know which location you mean and I agree it is not easy to find:

• As you made your way over the first pyramid, where the chapter begins, head west.

• You will then enter a larger pyramid site, with several small groups of enemies between.

• Proceed west until you reach the burnt down bridge, which would usually lead you to take a high path around the north.

• Instead of walking the north path, take the south path.

• You will reach a rectangled square, where is a way to west again, that ends on a slightly higher round platform. From that there is a way going south again

• This path ends in another rectangle platform with foes and a treasure chest at the south bottom.

• In the south west corner is a cauldron with a fire burning in it. This is "the ritual".

As you tap on it while standing next to, the fire should extinguish (i'm not sure about that anymore), and your quest should be marked as done and you can return to Liana claiming your reward.

Usually quest targets have a multicolored circular marking around them. Due to the color of the sandy ground and weak lights in that part of the map this marks can be easily overseen and the cauldron misjudged as simple decoration.

As soon as you mastered this quest once, you may take it again as an optional daily. On all following runs if you have the option "track target" active it will automatically point to the cauldron helping you to find it again.

However finding it the first time you have to do with out "track target" and I agree especially if you adjusted your display brightness rather low or very high, the marking around the cauldron is hard to see.