@Yukino welcome to DQ Forums!
that is a Crystal Legend Item. a Crystal Legend Items will only have 1 Crystal Affix (Cyan). Crystal Affixes are triple value, except for the 500 HP/MP on Hit Crystal Affix, which is only double.
Epic +15% Critical Chance (Orange) will be Crystal +45% Critical Chance (Cyan).
I believe there is a 1% chance for Legend Items to drop as a Crystal Legend Item (only if the Legend Item has one of the 20 affixes on the Crystal affix list).
higher Luck can improve your chances of better Crystals & Myth Stones dropping. higher Tier monsters have a better chance of dropping better Loot also.
at every floor 100, you can get better Crystals & Myth Stones at the cost of not getting a lower CS & MS.
at floor 100, Calcite/Hero stops dropping, 200 Angelite/Mentor, 300 Quartz/Protest, 400 Diamond/Boon, & 500 Larimar/Gift. but then your Rare & Ultra Rare Crystal & Myth Stone drop rates go up a little bit.
when you get to floor 200, what do you want to do?
Farming: put Luck & Gold Find on your Build for better Loot to Craft better Items later.
Climbing: at floor 200, either wait until you get a random Cartographer to drop a Challenge Map for the next floor, or go to the Shop and buy a Challenge Map for the floor you are on. every Challenge Map has a Cartographer on the Green Dot. when you defeat a Cartographer, it drops a Challenge Map for the next floor. these Builds just need good defense and lots of damage.
Ascending: these Builds are for getting Perks. Perks help improve your Farming. you don’t really need them, but they give really good boosts for Farming. you only need to farm floor 100-110 for Experience, as experience from monsters stops going up at floor 100. putting +200% Experience on your Build will help you get lots of experience. there are 6 Perks.
Battle Arena/PVP: this is where you fight other Players Characters with your Characters.
hope this helps.