can use object editor but trigger method =
event = a unit gains a item
condition = item being manipulated equals to sword
action hero - add 3 strength to hero manipulating item
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event = a unit loses a item
condition = item being manipulated equals to sword
action = remove 3 strength to hero manipulating item
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bugs = if you have a inventory system that does not allow a archer to gain a sword
it will -3 str from the archer every time he tries to pick up the sword