(You have to know, this system revolves mostly on attack bonuses and penalties. So yes, you can attack with both weapons in the same turn, but the rusty sword itself for being rusty has a damage penalty [you only will know after you get it identified once you return], the dual attack gives a -1 damage penalty for each weapon, and a -10% base accuracy debuff on whichever weapon you choose. so yes, you can use both in the same turn.)
(also, there are retreating attacks (sorry for missing so much in OP, hard to include all this, or come up with all of these battle scenarios. Deal with me here) where they get a -2 damage penalty, but allow you to get out of reach of the enemy you jumped away from, giving them another roll for who they target, and if you it will do a charging attack with a -2 damage penalty) (all this is to avoid a simple "I attack, they attack, I attack, they attack" pattern until you're all dead. choices are what I''m striving for. I'll toss these in the OP, and others as they come up.)
But, I assume that for this turn Rodri is attacking a leg, Jerri will spell range- then attack it, and Lia will do a retreating attack.
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Rodri swings his hammer at the golem, but as the hammer draws close it raises it's left (boulder) hand, knocking the hammer ever so slightly off balance. (6 damage) to smooth golem.
Jerri Jumps back further and fires off another blast at the golem. (2 damage.)
Lia Quickly sidesteps, lunging her spear at the golem. But it swings it's arm towards the spear, smacking it in the side and knocking it out of her grasp. (weapon dropped) oh dear...
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The golem quickly rebounds it's arm, swinging into Rodri's gut, knocking him back. Rodri's HP- 1 (don't worry, your lethal is still at full)
(I have to tell you, this golem is getting very lucky rolls.)