The artefacts can be found on the adventure map and can greatly improve the heroes’ performances during the battles or on the adventure map.
Each hero has a limited amount of slots (9 slots, amongst them, the head, the armour, the legs or the neck) but an unlimited back bag. For example, you can find on the adventure map a sword, an axe and a staff but you won’t be able to equip a hero with all of them at the same time and thus, you will have to choose which one is in the right hand of the hero and which ones remain in the bag. You can always rearrange your artefacts before you engage in a combat though.