There are no dual-wielding a.k.a. two-weapon fighting rules in Stars Without Number. SWN is a fairly direct ancestor of Basic D&D, which predates two-weapon fighting in the evolution of D&D rules, so that's not surprising. Other retroclones and OSR games in the Basic D&D lineage tend to lack two-weapon fighting rules in general.
However, there's one BD&D-descended game that does contain TWF rules: Adventurer Conqueror King System (ACKS). In a blog post at Bernie the Flumph titled “Stars Without Number: House Rules”, he details three house rules his group has used successfully in a SWN campaign, which includes borrowing the ACKS dual-wielding rules:
- Dual wielding two melee weapons or two ranged weapons gives you a +1 to hit. Use the damage for your main weapon. (Also stolen from ACKS.)
I have played enough ACKS to generally endorse this rule's effectiveness and balance, and I know that SWN and ACKS are close enough rules- and balance-wise that it should be easily portable. And since someone has actually done it and had it work, you don't have to take my word for it!
This rule doesn't get you the fanciness of having two monoblades that are distinct in their effect in the same round, but at least you would get a +1 to hit and might be able to switch which one is the “main” weapon from round to round to capitalise on their different strengths. Talk to your GM about it anyway — the fact that the rule isn't spectacular in its effect might make it more attractive to your GM.
