Subterranean Assault: The 11th-Edition Tyranids Burrowing Detachment

It has four parts, and the first is the one people underrate.

Every Tyranids model in your army re-rolls Hit rolls of 1. Not just burrowers, not just units arriving from Reserves. That is a flat, unconditional accuracy floor across the whole force, with no keyword or Synapse gate on it.

The rest builds the tunnel network. Each time a Burrower unit is set up from Reserves, you place a 40mm Tunnel Marker within 1" of it and more than 3" horizontally from all enemy units. From then on, when you set up a unit from Reserves in the Reinforcements step of your Movement phase, you can place it wholly within 9" of one of your Tunnel Markers and more than 6" horizontally from enemies, rather than the usual 9" from the enemy. Markers are fragile: if a non-Aircraft enemy model ends any move within 3" of one, it is removed.

Finally, the keyword clause. Mawloc and Trygon units gain the Burrower keyword, and in the Muster Armies step you can pick up to 2 Trygon models to gain the Character keyword. The pack's own designer's note spells out why that matters: those Trygons can then be given Enhancements, and one of them can be your Warlord.

Six, all 1CP, and most of them care about Tunnel Markers or units that just arrived:

• Enfilading Emergence (end of your Movement) — a unit set up as Reinforcements this turn gains Sustained Hits 1 and Ignores Cover until the end of your next Fight phase. The payoff button for a well-timed arrival.
• Swarming Assault (your Charge) — a Monster unit set up as Reinforcements this turn lets friendly Tyranids units within 6" re-roll Charge rolls. This is how a Trygon drags the whole arriving wave into combat.
• Tunnel Network (end of your Movement) — a unit wholly within 9" of one Tunnel Marker and out of Engagement Range teleports to another marker, more than 6" horizontally from enemies. Your late-game objective grab.
• Replenishing Swarms (your Movement) — a unit wholly within 9" of a Tunnel Marker regains D3+1 wounds on one model, or returns up to D3+1 destroyed one-wound models. Tunnel Markers become healing stations for gaunts.
• Adaptive Optimisation (Command) — a Mawloc or Trygon unit gains the Synapse keyword until your next Command phase, patching a synapse hole where your burrowers landed.
• Retreat Below (end of your opponent's Fight) — one Tyranids unit, or up to two Burrower units, out of Engagement Range go back into Strategic Reserves to come again.

• Trygon Prime — Trygon model only. The bearer gains the Synapse keyword and its melee weapons get +1 Strength and +1 Weapon Skill. This is the reason to use the Character clause on a Trygon in the first place.
• Tremor Senses — after both players deploy, redeploy up to three friendly Tyranids units, and you can put them into Strategic Reserves regardless of how many are already there. Elite counter-deployment, and it stacks with a reserves-heavy plan.
• Vanguard Intellect — Tyranids model with Deep Strike only. The bearer's unit can Deep Strike in your first, second or third Movement phase regardless of mission rules, so a mission that delays Reserves doesn't blunt your alpha strike.
• Synaptic Strategy — once per battle, target the bearer's unit with Rapid Ingress for 0CP, even if you already used that stratagem on a different unit this phase.

(Points move with dataslates; confirm them in the app.)

• Trygon / Mawloc — the two units the detachment rule hands the Burrower keyword to, which is what makes them your primary Tunnel Marker generators. A Trygon made a Character carries Trygon Prime and can be your Warlord; a Mawloc brings its own terror on arrival.
• Raveners — burrowing melee that arrives next to a marker. The Faction Pack added the Vanguard Invader keyword to Raveners alongside Mawloc and Trygon, and reprints their datasheet.
• The Red Terror — an Epic Hero the pack prints in full, carrying the Burrower keyword on its own datasheet rather than from the detachment, so it lays a Tunnel Marker when it arrives too, and a Subterranean Hunter ability that slips it back into Strategic Reserves at the end of the Fight phase.
• Termagants — cheap bodies that Replenishing Swarms tops back up near a marker, and exactly the sort of unit you want arriving on a tunnel to hold ground.
• Tyrannocyte — a delivery organism for whatever you want arriving as Reinforcements to fire Enfilading Emergence.

Take it when your collection leans on Trygons, Mawlocs and Raveners and you enjoy playing the Reserves game: a light board presence early, then a coordinated eruption in the middle of the enemy line. It's also quietly the most generalist-friendly of the pack detachments, because the re-roll of Hit rolls of 1 applies to every model you own, whatever else your list is doing.

The weakness is the Tunnel Marker network itself. Markers evaporate the moment an enemy model ends a move within 3", so a fast opponent can dismantle your infrastructure before you use it. Place markers where the enemy has no reason to walk, and don't build a plan that needs a specific marker to survive two turns.

Sample gameplan: put your Burrowers in Reserves and hold a light footprint on the board, using Tremor Senses after deployment to shuffle up to three units into Strategic Reserves once you've seen the enemy setup. Bring the Trygon in first so its Tunnel Marker anchors the network, then arrive the rest of the wave wholly within 9" of that marker. Fire Enfilading Emergence on your best shooting unit and Swarming Assault off the Trygon so everything charges with re-rolls. From there, use Replenishing Swarms to top up gaunts sitting on markers, Adaptive Optimisation if you need synapse where you landed, and Retreat Below to pull a Burrower out and repeat the trick.