Originally Posted by
Aegwymourn
Actually our hobby group believes it falls under the "whomever's turn it is decides which order things that happen at the same occur." I cannot remember which page of the book specifies it but we find that is the best interpretation until it is specifically in a FAQ update.
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Holy ...
How did I miss that??? [EDIT: Thanks!] You're thinking of page 9, which states:
While playing Warhammer 40,000, you'll occasionally discover exceptions to the general turn sequence laid out here, when things are worked out as they occur rather than in any strict order. At other times, you'll find that both players will have to do something at the same time. When these things happen, the player whose turn it is decides the order in which the events occur.
So, uh, apparently you don't roll for it on each occasion. The player whose turn it is decides whether to challenge and then roll for MSS, or roll for MSS and then challenge. I don't think that affects the advisability of keeping a low-cost character around any high-cost character who is going to be taking on a scarab lord, though. It can be used as a shield to keep your high-cost character from suiciding in a challenge, and as a sword to keep either isolate the scarabs or neutralize the lord's attacks.