Nether Scroll of Azumar

From Candlekeep Mysteries, page 210.

Description
Scroll, legendary

Unlike most scrolls, a Nether Scroll of Azumar is not a consumable magic item. It takes 30 days of concentrated study — at least 8 hours per day — to attempt to understand this scroll. After completing this study, you must make a DC 25 Intelligence (Arcana) check. If this check fails, you take 16d10 psychic damage, and you can attempt the check again after another 30 days of concentrated study.

When you succeed on the check, you gain the following benefits:
 * Your Intelligence score increases by 2, to a maximum of 22. Once you gain this benefit, you can't use this scroll to increase your Intelligence again.
 * You gain advantage on saving throws against spells and other magical effects.

When you gain the scroll's benefits, a stone golem magically appears in an unoccupied space within 60 feet of you and acts as your ally. If you die, the golem turns to dust.