Dark powers might be used by many for basic advantage, but it is in the spells themselves that the true darkness shows. Such magic, for which there is much, encompassing the misery and mastery of others, can replace some or all spells which are known by a spellcaster, whether an actual warlock or not. Each one is tainted of course since all are rolled with dark magic side-effects. Any with the (dark) note should be made especially sure to be portrayed as one of ruin, rather than its normally possible beneficence or wonder.
1st Level: Command, Cure Light Wounds (dark, reversible), Detect Evil, Detect Magic, Light (reversed), Protection from Evil, Remove Fear (reversed), Resist Cold, Sanctuary (works via fear rather than sanctity), Pass without Trace (D), Jarring Hand*, Manipulate Fire*, Shocking Grasp*, Sleep* (dark dreams)