Hanuman's greatest feat during the battle
of Lanka was to bring back the herb that cured Lakshman
from a fatal wound. He flew al the way to the Himalayas
to find it, harassed by many demons, such as Kalanemi. Because
Indra was confusing him, Hanuman could not find the herb
and finally brought the entire Drona Giri mountain, on which
the herb grew, to Lanka.