Mythic Heroes - Nexus Gate - Toils of War

UPDATE: a guildmate brought to my attention the solution for my previously mentioned issue. You must use the left-facing cannon to destroy the barricade in front of the boulder while using the up-facing cannon to destroy the barricade to progress.
If someone figures out how to get everything in one playthrough, let me know. That one spot in front of the boulder that has to be blown up is using a gunpowder that I can't afford to waste in a single playthrough.
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