Assassinate Adeline gets advantage on attack rolls against any creature that hasn't taken a turn in combat yet. 

Petrifying Gaze. When a creature that can see Adeline's eyes starts its turn within 30 feet of her, she can force it to make a DC 16 Constitution saving throw if Adeline isn't incapacitated and can see the creature. If the saving throw fails by 5 or more, the creature is instantly petrified. Otherwise, a creature that fails the save begins to turn to stone and is restrained. The restrained creature must repeat the saving throw at the end of its next turn, becoming petrified on a failure or ending the effect on a success. The petrification lasts until the creature is freed by the greater restoration spell or other magic.

Unless surprised, a creature can avert its eyes to avoid the saving throw at the start of its turn. If the creature does so, it can't see Adeline until the start of its next turn, when it can avert its eyes again. If the creature looks at Adeline in the meantime, it must immediately make the save.

She commonly wears a white porcelain mask over her eyes. Only when the mask is removed, or taken off by Adeline, does she gain this feature.

If Adeline sees herself reflected on a polished surface within 30 feet of it and in an area of bright light, she is, due to its curse, affected by her own gaze.

Multiattack. Adeline makes either three melee attacks--two with her snake hair and one with her shortsword--or two ranged attacks with her longbow.

Snake Hair. Melee Weapon Attack: +8 to hit, reach 5 ft., one creature. Hit: 9 (2d4 + 3) piercing damage plus (4d6) poison damage. On a successful hit, instead of just normal poison damage, she can choose one of the following types of poison:
      Dead Eyes: (Once per day) Target must make a Con save +16 or become blinded.
      Draining Touch: (Once per day) Target must make a Con save +16 or gain a level of Exhaustion.       

Shortsword.  Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 4) piercing damage plus 15 (2d8+3) poison damage.

Longbow. Ranged Weapon Attack: +7 to hit, range 150/600 ft., one target. Hit: 6 (1d8 + 4) piercing damage plus 15(2d8+3) poison damage.

• Fast Hands Adeline can make a Sleight of Hand check, use her thieves' tools, or take the Use an Object action. She can essentially take this bonus action to take her mask off, thereby granting Petrifying Gaze as a bonus action.

• Commanding Strike Once per day, she can command an alley who fails with a weapon attack to reroll the attack.
• Uncanny Dodge When she is hit with an attack she can see, she can use her reaction to halve the attack's damage.

• Legendary Resistance. When Adeline fails a save of any kind she can choose to succeed instead.  (3x per day)