The Gambler

The Drow man in the corner, shuffling a deck of cards. The human woman behind the bar, shuffling cups, and giving a knowing, albeit sly wink. The Gambler is a man who, for all means, doesn't lose. They give their luck a shot on the greatest challenge; a bored deity, a fiend, a fey, whoever's willing to take up the challenge. They need only accept, and the play's are made. This subclass introduces a couple of concepts I've had rattling in the old brain cage. Will you take the chance?

Showdown

When you pick this subclass at 1st level, you're able to make your spells more potent, at the cost of them fizzling out at a chance. You use playing cards, including the Jokers, instead of the dice class to deal magic damage. Physical attacks are unaffected. Ace equals 1, Jacks equal 11, Queen equals 12, and Kings equal 13. Jokers cause the spell to fizzle out. You cannot shuffle the deck until either a long rest, or after a Joker gets flipped. 

Roulette Points

When you gain this subclass at 1st level, you can manifest your luck in miraculous ways. You gain a number of Roulette points equal to your Warlock level. You regain these points during a Short or Long Rest, or by using a spell slot (Up to 5th level) to gain them back. 1st level= 1 Roulette point, 2nd level = 3 Roulette points, 3rd level = 5 Roulette points, 4th level = 7 roulette points, and 5th level = 9 roulette points. You cannot gain back more than your maximum.

Joker's Bluff

 At 1st level, you gain the ability to manifest your luck as armor around you. You can use a Bonus Action to use 1 Roulette Point; Add your Charisma Modifier to your AC for 10 minutes. You can dispel this ability using a Bonus Action, but you cannot use this ability again while this ability is still active.

Gambler's Foresight

At 6th level, you learn to read people's intents, in the midst of combat. As a bonus action, use 4 Roulette Points; gain advantage on your next Spell attack or Ability Check. You can only use this ability once per Short or Long Rest. You also gain proficiency in WIS (Insight) Checks

Final Gambit

At 10th level, you channel your luck into a burst of energy, leaving you vulnerable afterwards. You can, a Bonus Action, use 7 Roulette Points; deal double damage on your next spell attack this turn, but you gain vulnerability to all damage until your next turn.

All-In

At 14th level, your luck is so powerful, it bends reality to ensure damage to your foes. You can use a Bonus Action to use up to the remaining amount of Roulette Points you have, and take necrotic damage, that cannot be reduced in any way, equal to half your remaining Hit Points, add those numbers together, and add that number to your Magic Attack Rolls and Spell Save DC until the end of your next turn. This effect has no effect on damage rolls.