Stolen Arcanum

Your patron is a being with reach and dominion over a grand variety of magic and power, and as such, it has lent you a spec of it and allowed you to learn magic you normally wouldn’t be able to perform. For example, your angelical patron may have power over divine magic, your great old one patron over wizardry magic, or your archfey over druidic. You gain the following benefits:

• Choose a spell of any class’ spell list, of a level not higher than your warlock spell slot level. It counts as a warlock spell for you, but it doesn’t count against your number of spells you know. You can cast it a number of times equal to half your proficiency bonus (rounded down), at a level equal to your warlock spell slot level, without expending a spell slot. You can also cast it by expending a warlock spell slot. Each time you gain a level in the Warlock class, you can change the spell for a different one of that same class’ spell list. 
• Choose a cantrip from that class’s spell list. It counts as a warlock spell for you, but it doesn’t count against your number of cantrips you know.