Passive.
Rubick gains 1 stack of Curiosity per level. Each stack grants +1 base damage, +0.3% Buff/Debuff Duration, and +2 Area of Effect bonus.
If Rubick sees an enemy Hero cast an ability within 1200 distance of him, he gains 2 Curiosity for 20s.
If an enemy that currently provides temporary Curiosity dies within 3s after taking damage from Rubick, he gains 1 Curiosity permanently.