In the game I’m translating from D&D, one of the NPCs is carrying a “Masterwork Shortbow” described only with: “+3 ranged (1d6/x3 crit, masterwork shortbow)”
What do you think a good way of translating that to an Open Legend extraordinary item is? I was thinking +1 agility or +1 advantage when using. Does that make sense, or any other suggestions?
Giving it the Deadly feature found in Chapter 9 should reasonably emulate a +3 bow. I’d probably go with tier 1 or 2.
Giving a +1 to Agility would be a bit much.
Advantage 1 is equal to roughly 2.5, so Deadly 1 would be good. You could go as far as Deadly 2, but that might be a bit much.
Actually, given the x3 crit, Deadly 2 would be just about right for a translation.
If you really wanted to go crazy, you could allow it to give the feat lethal strike , so that up to 5 damage dealt is Lethal Damage. If you did this, probably keep it at Deadly 1 though.
I like that - Lethal Damage and Deadly 1. I actually already gave him one lethal strike (we had to stop mid-battle last night) but not the additional advantage. Even with Adv 2 (focus and attack spec.) he wasn’t able to do much to the barbarian with 20 Guard (in battle trance), so this fight is feeling a bit grindy still, though using some of the community suggestions really made things easier (including the macro quick bar, @Great_Moustache, thanks!)
That said, I don’t really understand the attribute bonus - which property of extraordinary items does that fall under? Most items don’t seem to have this, though the Legendary “Giant’s Bane” does:
Weapon (Longbow), Powerful 2, Slaying (giants), Agility +1, Perception +2, Intelligent
Is that spelled out anywhere, or just GM discretion?
If you give the full thing of Lethal Strike, it would gain an addition advantage from an ally being adjacent to the enemy (unless you already give out that advantage for flanking anyways).
Actually, that’s why I did it - forgot that detail, the barbarian burst through a door where he was waiting so I took it as “off guard”
from Chapter 9, doing in the Legandary Items section in Properties:
Attribute bonus/penalty - When wielding the item, the owner’s attribute is increased or decreased by the amount indicated.
and this note at the very top of Legendary Items is important:
Second, they can confer such immense and unique powers that they often cannot be easily quantified with a wealth level.
That also triggers Lethal Strike, being surprised or unaware of the attack.
OK, so it is really reserved for legendary items, not your “every day” extraordinary ones 
correct, that is a pretty big bonus to modify.
EDIT:
B/c not only does it increase the dice pool/size you roll, but it gives you access to higher PL of boons/banes, and even access to feats you might not have been able to get.