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I just remembered something. The Necron Monolith has that rule where it negates the effect of Dark/Bright Lances. Before, we could only get a glancing hit and hope it dies with a roll of a 6. Now with 5th ed, a glancing hit cannot destroy a vehicle. It's a skimmer so we would need a 6 to hit it with any type of grenade...but I doubt anything would get close enough to it and live, since it just spits gauss death at everything...What do we do now?
Ignore it, avoid it, and kill all the other 'crons for a phase out.
Plus if the 'lith is being used for teleporting and WBB rolling on the 'crons, then it isnt putting out as much firepower....
Herald of the Colonel; Festooned with pistols, riddled with vermin, and finger lickin' good...
Ajay29 is right, avoid it and go for phase out.
However, if you must, consider ramming it.
Everything I have told you, even this, is a lie.
The quickness and ferocity of Dark Eldar close combat should let you be able to achieve a phase out without having to worry too much about the Monolith. Get into combat with the Necron units, and let your Wyches/Agonisers/Incubi/HQ tear them a new one with relative ease. Remember that units locked in close combat cannot be targeted by shooting, so that's also your safest location to be.
I also ignore it. Its not easy at all - a good necron player knows how to manage his phase out but every once in a while you have to find ways to orchestrate your forces and make sacrifices that will help you win. You won't always be able to ignore the monolith so its not as easy as it sounds.
The last game I shot a lone Archite into a huge necron warrior squad with a necron lord in it. My Archite hit the squad where I knew the Necron lord would easily be within 6" of the Archite so the 2 independent characters ended up in base to base contact (independent characters moving first in a counter charge). I placed all the Archites attacks on the lord (killing him) and luckily only five warriors hit back (which I saved and survived).
In the following necron turn they teleported out of close combat to the monolith in a tight formation and rapid fire the Archite to death.
In my turn 3 ravagers and 1 squad of wyches kill enough necrons to force phase out with no wbb rolls to save from. Disintegrators and a lucky sweeping advance did all the work in one turn.
Other than that give a wych squad all haywires. You'll hit with the grenades on a 4+ and pray for "6's" for the penetration. Then pray for a "5" or a "6" on the damage table. It would be a lot easier if the monolith didn't move so you'd get auto-hits but thats about it.
"On a hunch, I melted them down and inhaled the fumes and read the dark eldar codex again, AND FOUND A BUNCH OF NEW RULES HIDDEN BEHIND THE OTHER WORDS..." [Gardeth on modelling & interpreting the DE Codex]
A nice little tip if you're using a squad of witches as tank-hunters like this is to give their succubus the goblet of spite, that way they'll hit on a 3+ no matter how fast a vehicle's going. Makes them a bit more vulnerable in CC with other infantry mind, so it depends how specialised for this role they're gonna be
Nurse by day, Haemonculus by night
I was slightly worried when i found out are heaviest weapons can't destroy a Monolith =[.
But like many people are saying ignore the Monolith and compress all you're fire onto phasing the opponent out with a number of Lances,Disses,Agonisers..etc it shouldn't be to hard.
In a controversy the instant we feel anger we have already ceased striving for the truth, and have begun striving for ourselves.
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As a Necron player, I'll support what everyone else is saying here. Ignore the Monolith, you have far better options for killing Necrons.
Necron Warriors are far and away the weakest unit in the army, but they're also a necessity, both for objective claiming and for preventing Phase Out. (Plus, they're the only troops choice.) Concentrate on them and any Destroyers that you see, and you should clean up nicely. If the Necron player was foolish enough not to bring a Lord with a Ressurection Orb (or moved his warriors out of it's 6" range), then you should give very serious consideration to turning those Dark Lances on Warriors - normally a bad choice for other armies, but they'd prevent WBB rolls, which also means they can't be recycled through the Monolith.
Aside from that, high S weaponry that can floor a lot of models is always a good thing.
As was already mentioned, close combat is the key here. While 5th did improve the Monolith, they made Initiative a far better stat, thanks to combat resolution. Most Necrons are not fearless, and are initiative 2. Aside from that, their basic stats match normal SM's - something any DE combat squad can easily annihilate. Beat them in combat and make em fail their LD test - after that, it's almost assured you'll overrun. WBB rolls are NOT granted for models killed in Sweeping Advances, and that is the best weapon in your arsenal.
Speaking to trying to reduce the Monolith's shooting by foricng the Teleport/Recycle... nah. Don't try that. It'll probably end up happening anyway, but in all honesty, Arc Flux is far more dangerous to a DE player than the Particle Whip is. The Monolith can always move and fire one of those two guns, but never both. The Particle Whip is a high-strength, low AP large blast, that'll likely obliterate a single squad not in cover, assuming it hits. Arc Flux, on the other hand, targets every squad within 12" of the 'lith, with a 5/4 multi-shot gun. Against T3, 5+ save models, it'll break multiple squads at a time. And that's the gun it gets to use even if it uses the Teleporter.
Rather, assume the Necorn player will use Arc Flux and the Teleporter every turn. It's simply a better choice against DE lists. So what do you do about it? Get a unit capable of fighting within 12-15" of what you can presume will be the Monolith's movement path. Because it only moves a max of 6", this shouldn't be hard to predict. The player will be stuck with three choices - 1) Don't move the 'lith, allowing the squad that pops out full movement options - which includes rapid firing guns. 2) Move the 'lith and pop guys out where they can be "safe" or 3) Don't teleport at all. Any of those three scenarios could potentially allow you to charge the unit that pops out - and that's a fight you should win.
Finally, don't let the Necron player cheese you. The Monolith is still a vechile and follows vechile rules; 5th ed did pretty decent damage to how it works. If it Deep Strikes in, it still counts as having moved "Crusing Speed" despite its other rules, which means no Arc Fluxing. (Can Particle Whip or Teleport, thanks to its special rules, but if it Teleports, the models can't move - that Teleporter follows all vechile disembarkment rules, including the 2" range from the hatch!) A lot of players, knowingly or unknowingly, still treat the 'lith like it's 4th, which makes it reasonably more dangerous the turn it arrives.