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do screamers have to be able to see a unit to do their cutting attacks
suppose i have them hidden behind marauderers and i want to cut attack a rattling gun. do i have to see them before hand?
After reading up on them it would appear not, and I couldn't see anything about it on the HoC FAQ. So my guess would be that you don't have to be able to see them beforehand as it doesn't state this in the slashing attack rules. You attack them by 'moving over them'
Correct. As with any shooting, you do not need line of sight at the beginning of the turn (for normal shooting, you need LOS during the shooting phase). If your screamers move over the enemy during the movement phase, they can use their cutting attack.
Arena of Death Champion: Nexim of the Guldskullz Tribe. Fear my wrath!