Halo Wars 2

In the Campaign lobby, select Mission 5, "Manifestation," and turn on any one of the scoring skulls (preferably Nightmare). Now turn on as many non-scoring skulls as you want to help makes things easier. It's recommended to use Bountiful Harvest, Emperor, Pain Train, and Sugar Cookies. Next, select the Legendary difficulty and begin the mission.

When the mission starts, fend off the initial Flood waves with your starting army and then begin constructing three Harvesters and two Power Extractors at the main base. The goal here is to upgrade the base to Level 2 as quickly as possible. Once that is done, go ahead and construct an Apex and a War Council, and then you can begin building your army of Engineers and Banshees (there should be six Engineers; the rest of the army should consists of Banshees). While these units are being built, focus on upgrading your base to Level 3, Advanced Logistics and Reinforcements at the War Council, and Air Upgrades and Banshees upgrades at the Apex. As the population max increases, continue to fill your army with Engineers and Banshees.

With a maxed out army, you can finally begin working on the primary objective. Move your army north and you will eventually be required to turn back south, destroy a Flood-infested mini-base, and build a Mega Turret after retaking the mini-base for your own. The Mega Turret, once constructed, will destroy a Flood blockage in the north and allow passage deeper into the canyon where you will encounter the Proto-Gravemind. Your next objective here is to destroy the monstrosity, but to do so, you will need to attack each of its carapaces and then the Flood-hives within. When this happens, the Proto-Gravemind will recede into the ground, and another opening on its topside will open up. Use your Banshee army and focus fire onto this grotesque opening.

After this happens, the Proto-Gravemind will enter a "critical mass rising" state, a percentage will appear at the top of the screen, and your objective will require you to build additional Mega Turrets around the map in order to attack the target and reveal another carapace. For the purposes of the "Before This Gets Out of Hand" achievement, you must not allow that "critical mass" percentage to reach or rise above 50%; if it does, you will miss the achievement. Luckily, this shouldn't be too much of an issue, even on Legendary. Because your army mainly, if not entirely consists of Aerial Units, you can easily move the Banshees around the map quickly to reach the designated zones for each Mega Turret.

Just keep in mind that at each Mega Turret location there is a Flood-infested mini-base. The Banshees will have to destroy the base before you can build your own and construct a Mega Turret. The Proto-Gravemind's critical mass percentage will rise from the moment it first recedes into the ground until the moment you've built a Mega Turret and have returned to the designated area around the monstrosity. It's at this point that critical mass percentage will begin falling back down to 0%. Once a carapace, the hives within, and the opening on the Flood's topside have been destroyed, critical mass will begin rising again. Repeat this Mega-Turret-returning-to-the-Proto-Gravemind process twice more and you will receive a new objective: locate the Forerunner construct in the southwest corner of the map.

When you arrive, destroy the Flood infestation covering the Forerunner construct and a Retriever Sentinel will appear before making its way towards the Proto-Gravemind on its own. Move your Banshee army towards the Proto-Gravemind, use the Sentinel's special ability () on the Flood mass, and then attack the opening on the Gravemind's topside one last time. After this is done, the mission will come to end and "Before This Gets Out of Hand" will unlock.

The Par Time for this mission is 30 minutes, and so long as you built your initial Banshee/Engineer army at the start of the mission in about 11-12 minutes, you should be able to finish the mission in 26-28 minutes with little trouble. Thus, having completed a mission on Legendary in under Par Time with at least one scoring skull active, "Banished Prowess" will unlock at the post-mission screen as well.