Cortez

Form Specific. You can only make attacks based on your form, so check the bonus action section for more info

Multi-attack.  Standard Form.  Cortez makes three Stab attacks and one Poisoned Hook attack.

Stab.  Standard Form. Melee Weapon Attack: +6 to hit, reach 15 ft., (1d6 + 3) Piercing damage damage. 

Poisoned Hook.  Standard Form. Melee Weapon Attack: +6 to hit, reach 15 ft., (1d6 + 3) Piercing damage damage and (1d8 + 3) poison damage. On a Critical hit, the enemy is Poisoned until the start of your next turn.

Concentrated Attack.  Standard Form. Melee Weapon Attack: +11 to hit, reach 15 ft., (3d6 + 9) Piercing damage. 

Headbutt. Snake Form. Melee Weapon Attack: +8 to hit, reach 15 ft., (3d6 + 3) bludgeoning damage. 

Charge.  Snake Form.  After using this, you can use Bone Spray during your next turn.

Bone Spray.  Snake Form. Ranged Weapon Attack: +8 to hit, range 30/45 ft., 2 targets. (3d12 + 6) bludgeoning damage.  You can only use this if you used Charge during your prior turn.

Bite. Pieces Form.   Melee Weapon Attack: +10 to hit, reach 15 ft., (2d6 + 9) Piercing damage damage. 

Cortez is a flexible skeleton and can manipulate shape.  This changes him up quite a bit.

Standard form.  This is your normal form.  It's pretty neat

Snake Form.   Any creature that touches Cortez in this form or hits him with a melee attack while within 5 feet of him takes (1d6) piercing damage.  Speed is Reduced by half in this form.  Cortez can only enter this form at 66 hitpoints or lower.

Pieces Form.  Advantage on Dexterity Saving Throws.  You gain a Hover speed equal to your walking speed.  Cortez becomes a Large creature and gains control of 4 Flying Sword (stat block) with the slightly altered stats in the Mythic Actions section.  They are summoned in squares where his original Huge body occupied and if they are more than 20 feet away from Cortez, they are stunned until they get within 15 feet of Cortez.  They act immediately after his turn.  Cortez can only enter this form at 33 hitpoints or lower and can't leave this form, except after completing a Short or Long Rest.  If Cortez is reduced to 0 hitpoints or fewer, the Flying Swords act like mundane swords.  

Altered Flying Sword stats.

Hit points 7.  AC 15.

Longsword. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 3) slashing damage.