This page will show you a few examples of key configuration for you to get inspiration
keys.yml
key1:# The item materialmaterial:IRON_NUGGET# The item custom namedisplay-name:"&bRusted Key"# The item lorelore: - "" - "&7A rusted key for a rusted chest"# The item enchantsenchantments:unbreaking:1# The item flagsitem-flags: - HIDE_ENCHANTS# The sources where the key should dropdrops:# A Minecraft vanilla zombieZOMBIE:amount:1# 8% chance to dropchance:0.08SKELETON:amount:1-2# 12% chance to dropchance:0.12key2:material:GOLD_NUGGETdisplay-name:"&dMaster Key"lore: - "" - "&7A master key for a master chest"enchantments:unbreaking:1item-flags: - HIDE_ENCHANTS# Other drop sourcesdrops:# A custom monster from MythicMobsSkeletalKnight:amount:2-3chance:0.5# A block of gold oreGOLD_ORE:amount:1chance:0.1