Billy

Cunning Action. Your quick thinking and agility allow you to move and act quickly. You can take a bonus action on each of your turns in combat. This action can be used only to take the Dash, Disengage, or Hide action.

Uncanny Dodge. Starting at 5th level, when an attacker that you can see hits you with an attack, you can use your reaction to halve the attack's damage against you.

Sneak Attack. Once per turn, you can deal an extra 3d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon. You don't need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn't incapacitated, and you don't have disadvantage on the attack roll. This damage is already added in the damage of weapons.

Spellcasting. Billy is a 3rd-level spellcaster. His spellcasting ability is Intelligence (spell save DC 14, +6 to hit with spell attacks). Billy has the following Wizard spells prepared:
Cantrips (at will): mage hand, message, shocking grasp 
1st level (3 slots): detect magic, disguise self, expeditious retreat, jump

Nightingale. Melee Weapon Attack: +7 to hit, reach 5 ft., 20/60 ft. thrown, one target. Hit: 6 (1d4 + 4) piercing damage plus 10 (3d6) sneak attack damage. 

Light Crossbow. Ranged Weapon Attack: +6 to hit, range 80/320 ft., one target. Hit: 7 (1d8 + 3) piercing damage plus 10 (3d6) sneak attack damage.

Ethereal Connection. The Nightingale always knows the location of The Wren. The wielder of The Nightingale can teleport directly to The Wren.