Ok so I'm working on Artifact challenge 7.1-7.4 where you have to get a 4* or higher Artifacts from Kaerok Castle with HP% as the main stat. Been at it for days now and burn through my Multi-battles every day with either no Artifacts won or the wrong main stat. Is there any way to increase the chances of getting an Artifact from a raid or am I going to just have to go at it for weeks until I luck out? Thanks!