Appearance: This pleasantly fragrant bush produces olive green berries resembling small figs. Each bush contains 3d12 berries.
Cultivation: The bushes are difficult to maintain. Any character wishing to cultivate the plant must first make a DC 15 Nature check (Druids have advantage on this check). If a character fails this check they must spend a week of downtime studying the plant before they can make the check again. If they do so, they make the next check with advantage. If they fail this 2nd check, they automatically fail any further checks on this or any other Brain Berry Bush.
On a successful check the character will be able to maintain the bush as long as it stays in a moderate temperature and is rooted in water. A healthy bush cultivated in this way will continue to produce 1d4 berries per week.
Consumption: Eating 3 of these berries results in a temporary +2 increase to a creature’s Intelligence score (up to a maximum of 20). The effect wears off after 3 days or immediately after a Greater Restoration spell is cast on the creature. Once the effect wears off the creature will fell disoriented and weak and will be inflicted by the poisoned condition for 1d4 hours (only a Lesser or Greater Restoration spell will end this affliction early). Eating more than 3 berries will not result in a higher intelligence bonus.
A player who eats 3 or more berries at one time must make a DC 15 Constitution saving throw. The difficulty of the save increases by 1 for each berry eaten after 3. On a failed save, the character becomes addicted to the berries.
Cumulative effects: If the character has been under the influence of the berries for 1 continuous week (without the effects having worn off for any period during that time) then the next time that character consumes 3 berries at once they will receive an additional +2 to Intelligence (up to a maximum of 20). For example, if a character has consistently been under the influence of the berries for one month (4 weeks), they would have a +8 Increase to their Intelligence score (as long as that does not bring their total score to over 20). If the character loses the Intelligence bonus granted by the berries at any time and for any reason, they will start back at +2 the next time they consume the berries.
Addiction: A character who is addicted to the berries will become increasingly agitated with the passage of time. Once the effects of the berries wear off the player will enter a rage for *d4 + X hours (where * is the highest total bonus to Intelligence the creature received as a result of the berries and X being how many weeks the character has been under the influence of the berries, with a minimum of 1). For example, a creature with a base Intelligence score of 12 who has been taking the berries for 3 weeks would receive a +6 bonus to Intelligence, meaning their rage would last 6d4 + 3 hours.
While raging the player will lash out and attack the closest living creature (friend or foe) and receives the same effects as the Barbarians rage ability (this acts as a Level 1 rage, regardless of the level or class of the character). A Greater Restoration spell would immediately end the Addicted Condition, but has no effect on a creature who has already entered the Rage.
If no other living creatures are near the character, he or she will seek them out. If the character is locked away in a room, they will furiously try to escape, causing injury to themselves in the process if they are not completely restrained.
Once the rage wears off, the character will feel sick, and take the poisoned condition for *d8 + X hours (where * is the highest total bonus to Intelligence the creature received as a result of the berries and X being how many weeks the character has been under the influence of the berries, with a minimum of 1). There is no known way to end this condition early.