Ash heart

Godless fortitude - No god or any of that power can predict this person, and so asking a god for advice having to do anything with this creature will always result in a wis save of 18 or take 1d6 phy damage.

Spellcasting - Can cast spells up to 9th level of wiz and warlock. All spells uses their own blood carving runes into his arm as he casts the spells. he does 1d8 for every level of spell he casts to himself up to level 5, than it becomes 1d10 per level above that where at level 9 it becomes 9d12 damage to himself, But all spells casted using this method add half that damage to himself to the damage he deals.

Any hit with ranged or melee spells from this requires a con save against his con+con modifier.

Action Name. Blood regeneration: as a action he can re-absorb the blood he casts gaining 2d10+con hp.

Action Melee Attack. Summon blood sword / cost 2d6hp to summon / 5ft, hit +14 / 2d8+con slashing [magical] ; Any attack with this weapon the creature must make a con save of 18 or take 1d8 poison damage and become poisoned.

Action Ranged Attack. Blood dart / cost 1d8 hp to summon / 60ft, hit +14 / 2d6 piercing damage [magical]

Multitrack, Action serge, 2 strikes per attack, multi casting

Blood wave; 40ft cone / cost 1d8 hp / dex save 18 or take half / 2d8+17 slashing [str 18 save or be pushed back 10ft]

Blood missel; 120ft / cost 4d6 hp / hit +14 / 2d10+17 acid [Advantage on next attack]

Blood heal; 30ft / dex 18 [damage and heal] 4d8+6 hp

Dash, Disengage

can cast haste as a bonus action

Shield ; +5 AC

Brace for impact ; half the incoming damage if not already halved

Hold person spell; can cast hold person as a reaction just before being hit by a melee attack that's non-magical.

4 legendary action that recover 1d4 at the start of every round

Legendary Action Name (Costs # Actions). 

[1] Extra attack or spell

[1] legendary resistance 

[2] for spell reaction

[3] for teleport 120ft

[3] change lair to have more blood, blood puddles can be used to fire blood darts.