As you have noticed, many character skills in this game have a certain magical attributes, elements which they are related to. There are 7 types of the elements: Water, Fire, Earth, Wind, Poison, Ice and Lightning. For example most skills of Blade Knight uses Wind element, but Soul Master has a full variety of elements. You can get resistance from these elements, by wearing corresponding jewellery. However, rings and pendants will not only protect you from their element, but also provide vulnerability to the opposite. For example – if you equip a Ring of Wind, you will receive a reduced damage from skills with Wind attribute like Twisting Slash, but you will start to receive an increased damage from skills with Fire attribute like Fire Scream.
The higher item level of a ring or pendant, the bigger the resistance / vulnerability. For example: ring of Wind +9 will give you 9% of wind resistance and 9% of Fire vulnerability. Also Rings of opposite attributes will deduct each other, for example: if you equip Ring of Fire +13 and Ring of Wind +13, your Fire Resistance will become 0, because Ring of Wind has Fire vulnerability.
In general, main goal of this innovation is to add variation to the game. So you could choose in which cases this or that jewellery will suit you better. For example equipping full set of Wind jewellery you will get a maximum protection from Blade Knights, but will become gradually weaker against Dark Lords.
I would like to remind that you can increase your jewellery item level with Fruits in a web-chaos machine up till +7, but soon we might have a new Jewel for leveling the jewellery, and skills which don’t have any attributes at the moment, will eventually get them.