There are 4 types of dragon artifacts.
1. Bleed charm.
It causes moderate bleeding damage overtime, with a 5% increase for every enemy you hit, capping at around 50%.
2.Attack power up charm
For every enemy you hit it increases your total damage by 10%, capping at a 100% attck boost, basically doubling your damage.
3.Defense power up charm
Increases your defense the same way as the attack power up charm.
Speed charms increase (max capping at) 50% attack, buster generation and movement speed.