What kind of list do you want to build? If you're going for a cheesy list that destroys your opponents, you can't beat a decurion, preferably with lots of tomb blades and a canoptek harvest or destroyer cult. If you want a fluffy list, a reclamation legion or
CAD is a good choice.
Your list is intriguing. It has a very wide variety of units, which means you can deal with pretty much any threat, but I worry that you will be overwhelmed since most of your units have some drawbacks that your opponent can exploit.
First of all, your unit choices. Almost all Necron units are decent to very good. But there are a few in this list that don't seem to work together too well.
First of all, the nightbringer. C'tan are regarded as one of the poorer units in the new codex, thanks to their random shooting attacks and weak defenses. That said, the nightbringer has some utility thanks to his gaze of death attack, which can deal ap2 wounds without rolling to hit. If you have your heart set on using him, I'd suggest getting another cryptek and putting him in a Conclave of the Burning One formation. Although it's expensive, it allows you to increase your C'tans defenses.
Next we have Imotekh. While he has been buffed, Imotekh seems to struggle in lower points games.
IMO, if you want to use him effectively, you kind of have to tailor a list around him (I'd be happy to show you a 2500 point list I built around him, but it would require getting a lot of models)
Next there's the monolith.
AFAIK this tank hasn't been that good since 3rd edition, but it's a great addition to any fluff list since it perfectly embodies the Necron feel.
All your other units are good choices, but I feel they don't have a lot of synergy. Lychgaurd are strong and tough but slow. Triarch stalkers are notorious fire magnets, and you don't have any units that really benefit from the +1
BS bubble. Both Warriors and Immortals are good, but Warriors edge out Immortals simply because there are better options than Immortals for their points (tomb blades), and Immortals can't take Ghost Arks. Wraiths are great, but they are the only fast unit in your list.
This brings me to my next point, mobility. Your list (except for the wraiths) is only going to be moving 6 inches per turn, and I worry that you'll have trouble getting your lychguard into combat. In addition, Necrons are a short ranged army that need a bit of mobility to support them.
One final issue is your lack of troops. Since you're playing a
CAD, you should take advantage of ObSec. I don't think one min unit of footslogging warriors and one min unit of footslogging immortals will be enough.
Sorry for sounding so negative, but your list does have some issues. Here is a list I made up, trying to use as many of your listed models as I could. To run it, you would only need to get 10 more warriors, a squad of tomb blades, and another cryptek (unless you have more models than listed above).
Decurion
Reclamation Legion
Overlord (Voidreaper, Phase Shifter, Phylactery, Res orb) 175 pts.
5 Lychgaurd (Sword and Board) 150 pts.
5 Immortals 85 pts.
20 warrors 260 pts.
3 Tomb Blades (shieldvanes, nebuloscopes, particle beamers) 72 pts.
1 Monolith 200 pts.
5 Deathmarks 90 pts.
Conclave of the Burning One
Nightbringer 240 pts.
Cryptek (nightmare shroud/solar thermasite) 125 pts.
Cryptek (god shackle/ veil of darkness) 100 pts.
Total: 1497 pts.
Edit: I wrote up tactics and then accidentally deleted them.
Just note that the nightmare cryptek has a 2+ rerollable armor save, that entire unit is toughness 8, C'tan can tank ap2 wounds thanks to
FnP, invuln, and gaze of death. Also the unit has a 1 use teleporter.
Also, put your overlord with the lychgaurd for a super tanky unit that will never* die.
*note: immortality not guaranteed
