An archfey patron was one possible sponsor for a warlock. If a bargain was made between a warlock and one of the archfey, the warlock's patron gave them access to certain powers, including a suite of spells.
Novice warlocks that were sponsored by an archfey patron had access to faerie fire, sleep, calm emotions, and phantasmal force. These warlocks, if they were somewhat experienced could cast both blink, plant growth, dominate beast, and greater invisibility. Master warlocks under the sponsor of an archfey could even cast dominate person and seeming.