Genshin Impact Trial of the Bastion Day 4 Guide (Three-Dimensional Front)

Stage IV of Trial of the Bastion, called “Three-Dimensional Front,” went live on September 10, 2026, and it is the first trial in the run that pushes enemies off the ground. The stronghold still has 20 HP and you still hold it for three waves, but the tutorial that pops up before the prep phase is about the Winged Halberd-Knight, and the on-screen warnings during the fight now include “Airborne Opponent Inbound” alongside the usual elite and surprise callouts.

Quick answer: Talk to Talalikhin in Nod-Khadar, pick Stage IV: Three-Dimensional Front, then build around Pulling Mechanism and Impact Shield to funnel the ground waves while Suppression Device: Faster Blaster and Explosive Barrel Device handle the airborne and elite spawns. A finishing score near 7700 clears all three challenge rating tiers in one attempt.

Before you can start Stage IV

Stage IV does not appear on its own timer alone. Each trial unlocks a day after the last one, and it only becomes selectable once you have completed the trial before it. If Stage III is still sitting unfinished, Day 4 stays locked no matter what the calendar says.

Requirement	Detail
Stage IV unlock	September 10, 2026, after clearing Stage III
Event window	September 7, 2026 to September 17, 2026
Adventure Rank	20 or above
Story gate	Archon Quest Prologue: Act III “Song of the Dragon and Freedom”
Story gate	“Gunfire in the Silent Lands” from Chapter VII: Act I “Everwinter Without Mercy”
Event quest	“A Grueling Combat Simulation” (opens the full event)

All five trials run inside the Shadow Realm, which is why you keep your firearm loadout instead of your usual party. You start at the event menu, teleport to the arena, speak to Talalikhin, then choose Stage IV from the trial list and hit start.

Mechanisms to build in Three-Dimensional Front

The mechanism pool changes per stage, and Day 4 leans on suppression fire rather than the ice and spike setups earlier trials handed you. These are the five pieces worth spending construction materials on.

Mechanism	What it does for this stage
Pulling Mechanism	Drags advancing enemies off their path so they stack up in front of your guns
Impact Shield	Blocks the lane and buys time near the stronghold approach
Suppression Device: Blaze	Sustained damage on the main ground route
Suppression Device: Faster Blaster	Higher rate of fire, best against elites and airborne arrivals
Explosive Barrel Device	Burst damage on choke points where enemies bunch together

Placement tiles show up as blue grids during the prep phase, and enemy path indicators tell you which lane the next wave uses. Aim at anything you have already built and the F prompt lets you remove it, showing the value tied to that structure so you can rebuild elsewhere between waves.

Stronghold defense screen with the F Remove prompt shown while aiming at a placed mechanism — Aiming at a built mechanism brings up the F Remove prompt so you can free the tile. Image: HoYoverse

How to clear all three waves

Read the Winged Halberd-Knight tutorial when it appears, then walk the arena before spending anything. The intro cinematic shows the layout, and the enemy path markers tell you which side the first group comes from.

Grab ammo from the supply crates on the field. Your assault rifle is the workhorse here, and its charged shot punches through a line of enemies, which matters because the opening wave still runs at you in a straight column.

Lay your first mechanisms along the main ground lane before the timer runs out. Pulling Mechanism plus Impact Shield near the stronghold approach keeps the wave in one clump; a Suppression Device covers the far end of the path.

Hold your position through Wave 1 and shoot rather than reposition. The Remaining counter at the top of the screen tracks how many are left, so you can tell when it is safe to reload or pick up more ammo.

Combat phase with an explosion near the stronghold and the remaining enemy counter on screen — The Remaining counter tells you how much of the wave is still coming while your mechanisms fire. Image: HoYoverse

Spend the construction materials awarded for clearing the wave on Suppression Device: Faster Blaster. This is the intermission that decides Wave 2, because that wave brings both elite and airborne opponents and you need something that keeps shooting while you deal with one target at a time.

Targeting prompt showing a placed device can be removed for 90 during the build phase — The removal prompt shows the value attached to the structure you are targeting. Image: HoYoverse

During Wave 2, prioritise whatever the banner announces. When “Elite Opponent Inbound” or “Airborne Opponent Inbound” flashes, switch to that target and let the mechanisms grind down the regular enemies behind it.

In the second intermission, tear down anything sitting on a dead lane and add Explosive Barrel Device coverage where enemies bottleneck. Removing and rebuilding costs you nothing but time, and Wave 3 is denser than the two before it.

Build phase between waves with the remove option highlighted on a targeted structure — Between waves, clear structures off lanes the next wave will not use. Image: HoYoverse

Play Wave 3 defensively and stay near the stronghold approach. Frag grenades clear grouped enemies fast, and pairing an Electro frag with the Cryo Grenade Launcher triggers a Stellar-Conduct reaction, though frags can lodge in walls if you throw from too far out.

Airborne Opponent Inbound banner appearing on screen during the final wave — The Airborne Opponent Inbound banner during Wave 3 is your cue to switch targets. Image: HoYoverse

Confirming the stage cleared and claiming rewards

The run ends on a Challenge Complete screen with your final score and checkmarks against each rating tier. A total around 7700 ticks every tier for the stage, so if all three marks are filled, you do not need a second attempt.

Rewards are not handed over automatically. Back out to the event menu, open Challenge Rewards, and claim each tier individually. Across the event you are collecting Primogems, Mora, Mystic Enhancement Ore, Sanctifying Unction, and weapon ascension materials.

Note: clearing Stage IV is also what unlocks the final trial, which becomes available on September 11, 2026. Leaving Day 4 unfinished blocks the last stage even after it appears on the schedule.

Why runs fall short on this stage

Ignoring the airborne callout. Ground-lane mechanisms will not cover a Winged Halberd-Knight, so that kill has to come from your firearm or a Faster Blaster placed to reach it.
Building everything in the first prep phase. Each cleared wave pays out more construction materials, and Wave 3 needs that budget.
Running dry on ammo. The supply crates refill you between waves and are easy to skip when you are busy repositioning mechanisms.
Standing too far forward. Stronghold HP only drops when enemies reach it, and drifting out of position lets stragglers slip past your line.

The whole trial takes under seven minutes once the layout is set, and the scoring is forgiving enough that a clean single run beats grinding retries. With Stage IV done, the last trial is the only thing left between you and the full reward pool before the event closes on September 17.