DIO's Diary can be acquired VIA killing the DIO boss, using a trowel and digging up DIO's area.
below here is what can it get's all stands
This Can be sold at poof for 50k
15 minutes - 1/5 chance
Uses:
use on Star Platinum to get Star Platinum (Over Heaven)
use on The World/Retro The World to get The World Over Heaven
Use on Whitesnake to get C-Moon
Use on C-Moon to get Made in Heaven/Made in Hallows Eve
Use on Shadow Pot Platinum to get Green Platinum
use on Crazy Diamond to get Craziest Diamond
Use On to Star Platinum: Heritage For The Future get Star Platinum Heritage For The Future: Over Heaven