Keen Hearing and Smell. The mastiff has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Second Wind

2nd-level Warrior feature

The sidekick can use a bonus action on its turn to regain hit points equal to 1d10 + its level in this class. Once it uses this feature, it must finish a short or long rest before it can use it again.

The sidekick can use this feature twice between rests starting at 20th level.

Improved Critical

3rd-level Warrior feature

The sidekick's attack rolls score a critical hit on a roll of 19 or 20 on the d20. 

Disengage

Raven can take the Disengage as a bonus action.

Chain Mail.

Made of interlocking metal rings, a chain shirt is worn between layers of clothing or leather. This armor offers modest protection to the wearer's upper body and allows the sound of the rings rubbing against one another to be muffled by outer layers. 13 + Dex modifier (max 2)

Extra Attack

6th-level Warrior feature

The sidekick can attack twice, instead of once, whenever it takes the Attack action on its turn.

The number of attacks increases to three when the sidekick reaches 15th level.

If the sidekick has the Multiattack action, it can use Extra Attack or Multiattack on a turn, not both.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 2) piercing damage. If the target is a creature, it must succeed on a DC 11 Strength saving throw or be knocked prone. 

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) slashing damage plus 2 (1d4) cold damage.

Second Wind

2nd-level Warrior feature

The sidekick can use a bonus action on its turn to regain hit points equal to 1d10 + its level in this class. Once it uses this feature, it must finish a short or long rest before it can use it again.

The sidekick can use this feature twice between rests starting at 20th level.

Disengage. 

Raven can take the Disengage as a bonus action.

Defender. The sidekick can use its reaction to impose disadvantage on the attack roll of a creature within 5 feet of it whose target isn’t the sidekick, provided the sidekick can see the attacker.

 Horseshoes of a Zephyr

These iron horseshoes come in a set of four. While all four shoes are affixed to the hooves of a horse or similar creature, they allow the creature to move normally while floating 4 inches above the ground. This effect means the creature can cross or stand above non-solid or unstable surfaces, such as water or lava. The creature leaves no tracks and ignores difficult terrain. In addition, the creature can move at normal speed for up to 12 hours a day without suffering exhaustion from a forced march