For example, "A 1st-level dragonfire adept begins with knowledge of one least invocation[...]. [...] See Draconic Invocations, below, for a list of available invocations." (Dragon Magic, p.25).
You can create magical darkness, as the darkness spell (PH 216).
Then there is the BiS feat:
BLEND INTO SHADOWS
You can draw from nearby magical shadow to cloak yourself in darkness.
Prerequisite: Darkness as a spell-like ability.
Benefit: As a swift action, you can spend a use of your darkness spell-like ability to make a Hide check, even while being observed and without cover or concealment. You must be within 10 feet of an area of magical darkness.
You also gain one additional daily use of your darkness spell-like ability.
(Drow of the Underdark, p.47)
Can the Darkness invocation fulfill the prerequisite for the Blend into Shadows feat?
I guess an argument would be that the feat requires a spell-like ability specifically called "Darkness".