The Mystic Stinger is a rogue that combines magic with ranged attacks, drawing upon arcane energies to strike with ruthless precision.  Unlike most magic classes, the Mystic Stinger relies upon its Dexterity score to generate the raw energy used for its magical attacks and abilities.

Spellcasting

The Mystic Stinger is able to cast spells from the Wizard spell list.
Spell progression follows the third-caster tree (see Arcane Trickster subclass).
Spells use the Dexterity modifier.
There are no school restrictions on what spells you can choose, as long as they are Wizard spells.
There are additional granted spell choices embedded within some of the abilities.

Mystic Strike

You learn the True Strike cantrip, and can use it more effectively than anyone.  The following features are now in effect:

• You can cast it as a bonus action on your turn, rather than as an action, and before or after your action.
• The effects of True Strike impact both this turn and the following turn, giving you immediate and subsequent advantage on your attack rolls.
• Your perfection of this cantrip allows you to use it without using your Concentration.
• You may, in effect, cast True Strike on every visible hostile creature in range, giving yourself advantage on each creature.  However, your sneak attack will only apply to the creature that you choose in accordance with sneak attack rules.
• This bonus action use of this Cantrip cannot be used to trigger other effects (i.e. additional attacks or cantrips).  It exists in isolation.

Cantrip Arrow

Starting at level 3, you can use a bonus action to cast a cantrip on a quiver of ammunition.  The following rules apply:

• Cantrip Arrow applies to no more than 10 arrows or bolts in the quiver at a time. 
• The cantrip damage stacks with any other damage bonuses from any other spell or ability.  For instance, the damage of Flaming Arrows will stack with Cantrip Arrow: Fire Bolt or Cantrip Arrow: Chill Touch.
• The Cantrip Arrow ability cannot be applied to the same 10 arrows more than once.  For instance, you cannot enchant the same quiver with Fire Bolt and Shocking Grasp at the same time.
• Each damage cantrip that you know can enchant 10 pieces of ammunition per long rest.  If you know 10 damage cantrips, you can enchant 10 sets of 10 arrows.
• The effects of the cantrips on the arrows scale with player level, per usual.
• This ability grants you the selection of one additional cantrip of your choice.

The Way of the Stinger

Choose Between the Following Options at Levels 9, 11 and 13:

The Wasp
You can use a bonus action to fly without using your concentration.  While this is active, the following effects are in play.

• You gain flight (with a speed of 10) for up to 10 minutes; you may cancel this with an additional bonus action.
• You have +2 to all ranged attacks while flying.
• You have +2 to AC for the duration of the spell.
• Any time a hostile creature attacks you with a ranged attack while in the air, you may use your reaction to fire a ranged attack or spell.
• Since this spell does not rely on concentration, no constitution saving throws are required if you are attacked.
• You may use this ability once, and it recharges on a short rest.
• While flying, you have advantage on all non-flying hostile creatures and can apply your sneak attack once per turn per usual.

The Scorpion
You have learned to imitate the scorpion in combat.

• You can add 1d12 poison damage to each ranged or melee attack.
• Whenever a hostile creature enters melee range, you can use your reaction to attack it with advantage with a ranged or melee attack.
• You can activate this feature once per short rest.
• You can learn one additional 2nd-level spell of your choice.

The Spider
You have learned to imitate the spider in combat.

• You can use your action to cast the Web spell, without using a spell slot or having it count against the spells you know.
• You can use your action to cast the Spider Climb spell, without using a spell slot or having it count against the spells you know.
• You can cast the Freedom of Movement without using a spell slot or having it count against the spells you know.
• Once you use one of these effects, you cannot use it again until you finish a short rest.
• You also learn one Cantrip of your choice.

The Way of the Scorpion

You have learned to imitate the scorpion in combat.  You can choose this at level 9, 11, or 13.

The Way of the Spider

The Spider
You have learned to imitate the spider in combat.  You can choose this at levels 9, 11 or 13.

The Way of the Wasp

You can use a bonus action to fly without using your concentration.  While this is active, the following effects are in play.

• You gain flight (with a speed of 10) for up to 10 minutes; you may cancel this with an additional bonus action.
• You have +2 to all ranged attacks while flying.
• You have +2 to AC for the duration of the spell.
• Any time a hostile creature attacks you with a ranged attack while in the air, you may use your reaction to fire a ranged attack or spell.
• Since this spell does not rely on concentration, no constitution saving throws are required if you are attacked.
• You may use this ability once, and it recharges on a short rest.
• While flying, you have advantage on all non-flying hostile creatures and can apply your sneak attack.

Wrath of the Stinger

You get two extra attacks per action.
You can caste Haste as a bonus action, and does not require concentration.
You can choose a 3rd level spell of your choice, and cast it once per short rest.

Stinger Swarm

You create a storm of attacks.  Once per long rest, you can unleash a Stinger Swarm.  Using your action, you can fire off up to 10 attacks.  These stack with the extra attacks gained at level 13, and can use Cantrip Arrows, sneak attack on the target of your choosing, and any other bonuses.  However, you cannot strike a single target more than twice.  This is a swarm of arrows for attacking many enemies at once, but not a single enemy ten times.  If any arrows are unenchanted, they become magical for the purposes of this attack.