Medium construct, neutral

Armor Class 15 (Natural Armor)
Hit Points (equals the defenders Con modifier+ your Int modifier+5 times your level in this class)
Speed 40 ft.

STR 14 (+2) DEX 12 (+1) CON 14 (+2)
INT 4 (-3) WIS 10 (+0) CHA 6 (-2)

Saving Throws DEX +3, CON +4
Skills Athletics +4, Perception +4
Damage Immunities Poison
Condition Immunities Charmed, Exhaustion, Poisoned
Senses Darkvision 60 ft., Passive Perception 14
Languages understands the languages you speak
Challenge 0 (10 XP)

Might of the Master. The following numbers increase by 1 when your proficiency bonus increases by 1: the defender’s skill and saving throw bonuses (above), the bonuses to hit and damage of its rend attack, and the number of hit points restored by its Repair action (below).

Vigilant. The defender can’t be surprised.

Steel Defender. In combat, the steel defender shares your initiative count, but it takes its turn immediately after yours. It can move and use its reaction on its own, but the only action it takes on its turn is the Dodge action, unless you take a bonus action on your turn to command it to take one of the actions in its stat block or the Dash, Disengage, Help, Hide, or Search action.

If the mending spell is cast on it, it regains 2d6 hit points. If it has died within the last hour, you can use your smith’s tools as an action to revive it, provided you are within 5 feet of it and you expend a spell slot of 1st level or higher. The steel defender returns to life after 1 minute with all its hit points restored.

Actions (Requires your bonus action)

Force-Empowered Rend. Melee Weapon Attack: +4 to hit, reach 5 ft., one target you can see. Hit: 1d8 + 2 force damage.

Repair (3/Day). The magical mechanisms inside the defender restore 2d8 + 2 hit points to itself or to one construct or object within 5 feet of it.

Reactions

Deflect Attack. The defender imposes disadvantage on the attack roll of one creature it can see that is within 5 feet of it, provided the attack roll is against a creature other than the defender.


Sources

Image – http://klubbsaga2015.wikidot.com/iron-defender