Yes it is - that is why I have asked people to help!
Thank you for the suggestions. I takes me longer to rework a monsters (at least most of the ones I have done so far) because I feel the need to look over its history and lore and then reflect how I can add that to the 5e version without adding to much complexity. But it is work I enjoy, so there is that.
PM me I have a personal 5E MM with custom monsters and variants. Mostly lower CR but there are a few at CR5-6. Its got 33 monsters/NPCs in it up to CR 13.
You just copy and paste and change the numbers around. A coupe of samples.
Yuan Ti Hand of Seth
Medium Humanoid (Yuan ti half blood) chaotic evil
Armor Class 18 (studded leather,)
Hit Points 136 (18d8+45)
Speed 30 ft.
Saving Throws Dex +7
, Con +6
, Wis +4
Str 15 (+4),
Dex 20 (+5),
Con 16 (+3),
Int 10 (+0),
Wis 12 (+1),
Cha 15 (+2)
Skills Deception+5
, Intimidation +5, Stealth +7 (advantage)
Senses passive Perception 11
Languages Abyssal, Common, Draconic
Challenge 9 (5000 XP)
Sneaky: The Hand of Sseth has advantage on deception rolls to disguise themselves and on stealth rolls
Magic Resistance: Advantage on saves vs magic
Skilled. A melee weapon deals one extra dice of damage when the Hand hits with it (included in the attack)
Equipment. Rapier, hand crossbow, 2 vials of poison (7d6 damage), disguise kit
Actions.
Multiattack. The assassin makes 3 melee attacks or two ranged attacks.
Rapier. Melee or ranged Weapon Attack: +8 to hit, Hit 11 (2d8+5) piercing damage + 7d6 poison damage.
Hand Crossbow +8 to hit, (DC13 con save, poisoned 1 hour/unconscious if failed by 5 or more)
Assassin Traits (Assassinate, Evasion, Sneak Attack) Page 343 MM
Yuan Ti Abomination High Priest
Medium monstrosity (shapechanger, yuan ti race), neutral evil
Armor Class 19 (natural armor, dark blessing)
Hit Points 72(15d8+24)
Speed 25 ft.
STR 19 (+4)
DEX 16 (+3)
CON 17 (+3)
INT 17 (+3)
WIS 16 (+3)
CHA 18 (+4)
Saves Constitution +6, Wisdom +6
Skills Deception +5, Stealth +4
Senses passive Perception 13
Languages Abyssal, Common, Draconic
Challenge 8 (3900 XP)
Magic Resistance: Advantage on saves vs magic
Yuan Ti Malison abilities (page 308 MM)
Blessing of Sseth. As a bonus action, the priest can expend a spell slot to cause its melee weapon attacks to magically deal an extra 10 (3d6) poison damage to a target on a hit. This benefit lasts until the end of the turn. If the priest expends a spell slot of 2nd level or higher, the extra damage increases by 1d6 for each level above 1st.
Spellcasting. The priest is a 11th-level spell caster. Its spellcasting ability is Wisdom (spell save DC 13, +5 to
hit with spell attacks). The priest has the following cleric spells prepared:
Cantrips (at will):
light,
sacred flame,
thaumaturgy
1st level (4 slots): bless, cause wounds,
cure wounds,
2nd level (3 slots):
hold person,
spiritual weapon
3rd level (3 slots):
dispel magic, spiritual guardians,
4th level (3 slots) Banishment, Death Ward*, Freedom of Movement*,
5
th level (2 slots)
Flamestrike, Insect Plague
6
th level (1 slot)
harm
*Already cast
Actions
Multiattack The Yuan Ti makes three melee attacks or two ranged attacks
Bite. Melee weapon Attack: +7 to hit, reach 5’ one creature. Hit: 7 (1d6+4_ piercing damage + 10 (3d6) poison damage
Scimitar. Melee Weapon Attack: +7to hit, reach 5 ft., one target.
Hit: 3 (2d6++4) slashing damage.
Drow Weaponmaster (gladiator reskin
) CR6
Medium Humanoid (any race) chaotic evil
Armor Class 19 (chain shirt, buckler,)
Hit Points 112 (15d8+45)
Speed 30 ft.
Saving Throws Dex +7
, Con +6
, Wis +4
Str 15 (+4),
Dex 18 (+4),
Con 16 (+3),
Int 10 (+0),
Wis 12 (+1),
Cha 15 (+2)
Skills Intimidation +5, Stealth +7,
Senses passive Perception 11
Languages Any one language (usually common
Challenge 6 (2300 XP)
Superior Magic Resistance: 13
Skilled. A melee weapon deals one extra dice of damage when the drow hits with it (included in the attack)
Equpment (all Drow), Boots of Elvenkinfd, Cloak of Elven Kind, +1 short sword, +1 chain shirt, +1 buckler, 4 dose drow poison.
Actions.
Multiattack. The weaponmaster makes 3 melee attacks or two ranged attacks.
Shortsword. Melee or ranged Weapon Attack: +8 to hit,. Hit 11 (2d6+5) piercing damage + paralysis (DC13 con save)
Hand Crossbow +8 to hit, 1d6+4+paralysis (DC 13)
Drow traits (page 128 MM)
Longbow (yuan ti form only) Ranged weapon attack +6 to hit, range 150/600ft, one target, hit 2d8+3 piercing damage+3d6 poison damage