Hi,

We played a first couple of missions of Imperial Assault this weekend, and i think my fellow Rebels are cheating me. They used Mak's Ambush ability to pull off impossible shots - through allied and enemy figures for example. I re-read the rules, and it seems there are only two cases he can actually benefit from Ambush - utilizing Covert and shooting around the corner due to non-reciprocal LoF. Am i correct?

They are absolutely misplaying him. Mak doesn't get LOS through figures from these abilities.

You are absolutely correct.

Yes, Mak still needs line-of-sight to his target in order to make a shot, and other figures in the way would block that line-of-sight unless they have some other ability to allow it, which they shouldn't have access to at the beginning of a campaign. The way his Ambush can be triggered is either when he's 4+ away from the target so his "Covert" makes him invisible to the target, or when he's shooting from a corner between two other figures or some other unusual situation where he can still trace line-of-sight out, but the target can't trace line-of-sight back to him.

Target Acquired is the ability which allows to ignore figures when drawing LoS, but that also exhausts, so can only be used once per activation (so it doesn't combo well with No Escape for example).

Ambush does nothing to lift any of the line of sight rules, Ambush requires that Mak has LoS to the target and the target does not have LoS to Mak (which can be because of Covert and the target being 4 or more spaces away, or Mak attacking between a wall/blocking space and a figure).