2 km
The reason why they'll be fine is because the Reapers don't have the power to bust through their multiple Void Shields (shields that send attacks into another dimension, and take minutes to go from broken to full power.) These things tank Teraton attacks, Reapers barely put out megatons.
And an Alpha + Psyker onboard would prevent any indoctrination.
English
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Oh, I see. I wasn't aware of the ships shielding capabilities, or firepower. In that case, you're probably right lol
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Yea, no worries. 40k is nuts. Hell, a Necron fighter could solo the Executor.