A Four-Leaf Clover is a type of leaves from a clover flower. Graham discovered one in a meadow in Daventry. In KQ1, he can show it to the leprechaun guards in the Land of the Leprechauns and they'll let him pass.
It is a member of the Trifolium family with an extra leaf, also known as a shamrock (although there is some dispute). This type of clover is supposed to bring good luck to its wearer. It is not, however, the same as a shamrock. The shamrock--the symbol of Ireland and the favorite of leprechauns--is a three-leaf clover, and not the same plant at all. This confusion between the two different plans is so widespread that, evidently, even the leprechauns of Daventry themselves get confused.
Behind the scenesEdit
In the original KQ1, this was known as the fourleaf clover (or the 4-Leaf Clover in the KQ1 hintbook map), in the remake its the Four-leaf Clover, in the Sega version its the "4 Leafer".
In real world a four-leaf clover is only a mutant aberration of a common three-leaf clover plant. Hence the shamrock and four-leaf would be the same plant. In the KQ univere they may be seperate plants.