WHat can he dropp?

Anne Laker
Knowledge: Agrakhan
Annolisa Rosie Goddess of Knowledge
Loot Table

The 'boss summon scrolls' have been removed from the game (circa March 2024 on console), and so the only way to get Agrakhan knowledge now is to talk to Anne Laker (node manager of Cadry Ruins) after obtaining all Cadry Followers Ecology knowledge.

From the BDO Console release notes:
"
Improved so that you can acquire Agrakhan knowledge from NPC Anne Laker at the Cadry Ruins under the following conditions.
Obtain all knowledge under [Knowledge] Ecology - Ecology of Valencia - Cadry Followers category (excl. Cadry Chief Gatekeeper)
"