Help designing a creature

[MonkeySage]

I've taken the project of adapting a scenario from a different game to d&d next. In that scenario, there was a monster, and I'm now trying to figure out how it should work out.
What i've got so far:

Large aberration, chaotic evil
Armor Class: 17 (Natural Armor +4)
Hit points: 6d10 (47)
Str 23 (+6) Dex 16 (+3) Con 15 (+2) Int 13 (+1) Wis 16 (+3) Cha 14 (+2)
Damage Resistances: Acid, cold, thunder; bludgeoning, piercing, and slashing from nonmagical weapons
Damage Immunities:Fire, Lightning
Condition Immunities: Charmed, Grappled, Petrified, Poisoned, Prone, Restrained
Senses: Blindsight 60 ft., Passive Perception 16
Languages: Telepathy 30 ft.
Challenge:
Incorporeal Movement
Partial Invisibility: The lurker appears as a misty figure without magical assistance. Attacks made against the lurker take disadvantage.
Horrifying appearance: When the veil of partial invisibility is lifted, and the lurker’s true form revealed, onlookers must make a DC ? Wisdom Save or be frightened for 1 minute.

As you can see, there are some blanks. Without the DMG, it will be difficult for me to fill in those blanks. But until then, I was hoping to get some suggestions, thoughts, etc. How does this thing look to you? What would you do to make it better?

I'm new to D&D next, and took on this project in hopes that it would also help me learn the system a bit more.

[Rfkannen]

Well, I don't know much about monster creation. But the question that arises to my mind are twofold, what is it/what is it suppose to do? And who are you sending it up against.

[MonkeySage]

The scenario I lifted it from was a call of cthulhu scenario. This creature was originally based on the Lurker in The Edge of Darkness. I'm adapting that scenario to this game. I'm not having trouble with the transition from ordinary people to low level adventurers, and it shouldn't be too hard to emphasize the fear this creature is supposed to elicit from player characters. The hard part is getting it's stats down.

The creature's actual appearance is intentionally left vague, it's origins are a total mystery. The creature came into this world via ritual summoning gone wry, the last remaining participant of which wants to hire adventurers to either kill or exorcise it.
It eats hearts, leaving perfectly round holes in it's victims. It also has talons, which couple with it's impressive strength are capable of piercing the skull.

[PAE_The_Boss]

The scenario I lifted it from was a call of cthulhu scenario. This creature was originally based on the Lurker in The Edge of Darkness. I'm adapting that scenario to this game. I'm not having trouble with the transition from ordinary people to low level adventurers, and it shouldn't be too hard to emphasize the fear this creature is supposed to elicit from player characters. The hard part is getting it's stats down.

The creature's actual appearance is intentionally left vague, it's origins are a total mystery. The creature came into this world via ritual summoning gone wry, the last remaining participant of which wants to hire adventurers to either kill or exorcise it.
It eats hearts, leaving perfectly round holes in it's victims. It also has talons, which couple with it's impressive strength are capable of piercing the skull.

I'd advise that you work backwards from the sort of encounter you want to have. What do you want the players to experience? Fear? Helplessness? Empowerment? Dis-empowerment?

If its just the stats you're having trouble with, work off of other similar-level creatures and vary the numbers just a little so that they represent the creature's nature a bit more.

The most important thing is just to keep it balanced with the level of the players it's going up against.