JBCrowson
Sage
If you want to stay with the engineering, could the magic latex be made into self turning tyres / wheels? The energy saving from that would be enormous and avoid horses or other draft animals that need food, shelter etc. Your roads would have to be up to scratch in enough of your world to make it worthwhile.
The magic rubber could make better catapult weapons e.g. greater range / accuracy. Could you make hard (vulcanised) rubber projectiles from it that are targetable to a specific person / race / species?
The magic rubber could make better catapult weapons e.g. greater range / accuracy. Could you make hard (vulcanised) rubber projectiles from it that are targetable to a specific person / race / species?