Legendary Resistance (1/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Ad'roc comes out automatically when his wearer enters combat though he cannot take actions on his own. The wearer of the Ad'roc's tattoo can sacrifice their action and bonus action to allow Ad'roc to take his full turn. Ad'roc can take his Legendary actions and resistances as described without the wearer's say so.  Otherwise on his wearer's turn, Ad'roc can move and takes the Dodge Action. If Ad'roc drops to zero HP, he returns to his tattoo. If the wearer dies, Ad'roc dies and returns to his (GM discretion) plane of existence. Adroc can be summoned by his wearer outside of combat at any time. Ad'roc can telepathically speak to his wearer and his wearer to him. Ad'roc can feel his wearers emotions and can hear but use no other sense of his wearer at any time.  . 

Multiattack.  Ad'roc can make two melee attacks. Choose from Bite, Claws, or Tail. 

Bite. Melee Weapon Attack: +4 (1d4+2), piercing damage.

Claw. Melee Weapon Attack: +4 (1d4 +2), slashing damage

Tail. Melee Weapon Attack:  +4 (1d4 + 2), bludgeoning damage

Alternatively. Ad'roc can use its action to do one of the following:

Frightful Presence. One creature of the dragon's choice that is within 30 feet of the dragon and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for until the end of its (the creatures) next turn.

Distract. Ad'roc can chose a target within 5 ft of him to buffet with his wings. Allies within 10 ft of Ad'rocs target can move an additional 5 ft in a direction of their choosing without provoking opportunity attacks from Ad'roc's target. 

Acid Breath, 1/short rest. The dragon exhales acid in a 15-foot line that is 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 1d8 acid damage on a failed roll and half as much on a save.