Fyreslayers tunnelling? New player

[Akorndr2]

Hey guys New player and New member. I've been reading a few posts on tactics for Fyreslayers who recently got a update to their pts and are cheaper and I keep coming across this idea of tunnelling and I don't know where to find this rule or tactic could someone point me in the right direction please. 

[Setlot]

It's an ability of the Auric Runesmiter on foot called Magmic Tunnelling.  Basically it allows you to keep the Runesmiter and one other unit in reserve and then bring them into play anywhere on the table at least 9" from the enemy in any of your movement phases.