Impassable or not?

The recent AOS World Champs 2022# saw the event organisers add "impassable" terrain comp rule to the event. This article discusses some of the nuances and implications of adding "impassable" to your event.

Background & History

The 3D terrain rules within AOS have been somewhat problematic since day 1. Fundamentally, the game is not really designed for use of 3D terrain, and the rules team seems to have ultimately opted for a combination of short streamlined terrain rules and "let the players work it out via common sense". Of course, in a highly competitive setting, "common sense" can be a problem where there is advantage/ disadvantage to be had via using exact RAW rules!

This has historically seen terrain rules exploited - such as a deep-strike shooting unit landing on top of a 15" tall terrain piece and blasting away with impunity, becoming effectively impossible to reach. Or immersion breaking moments where some huge base flying monster hangs off the side of a tiny flagpole and then skateboards down a wall to slingshot past some front line screen-blocker unit. Various terrain exploit interactions can and have created contentious and even "feel bad" moments in the game.

Impassable terrain can add some really cool and interesting tactical elements to a game (eg chokepoints), and can also 'solve' some of the 3D terrain exploit rules above. However, while adding impassable can 'solve' one problem, it creates a plethora of other downstream problems.

To Impassable or Not

So, should you - a new to scene TO - add Impassable terrain or not to your event? After all, the World Championships# did it, so it cannot be that big a deal right?

To be really clear "impassable" is definitely NOT part of the core rules, so adding in Impassable is a TO override on core rules. The game is not designed or balanced with impassable terrain included. There are SIGNIFICANT downstream meta winners & losers implications for the for the game if you do add in impassable as a comp rule to your event.

Winners & Losers

The main impact of adding impassable terrain is it inhibits movement around the table. In short, this creates significant advantages for armies/ units/ playstyles that are desinged to benefit from movement being inhibited, and massive disadvantages for armies/ units that want clear space and nice clean run at the enemy.

Meta Winners:

1. Sevireth, Lord of the Broken Warscroll with his buddy foxes:

The LRL Fox + Sentinals list is already a powerful list with long term proven success. The lists core aim is to use the Foxes extremely annoying movement shenangians to bottle up the opponent and buy extra time for the Sentinals shooting to blast the opponent off the table. Adding impassable massively increases the Foxes control efficiency at choke points