The Necrons have a very rigid feudal hierarchy dating back to the time when they were still Necrontyr, and it was made part of their most basic programming when they were upgraded into Necrons. Whereas Necron Lords only rule over a single Tomb World, a Necron Overlord may hold anywhere from 3 to a dozen Tomb Worlds in his sway. And as the Lords bow in service to their overlords, the Overlords of a Necron Dynasty kneel to the Phaeron, the SPACE EGYPTIAN ROBOT ZOMBIE KING OF KINGS for his word is law, more so now since there is no Triarch council to keep the different dynasties all on the same page.
Necron Overlords have a closely kept circle of advisors and viziers, consisting of high-ranking Crypteks and lesser Necron Lords. This 'Royal Court' of knowledge and influence not only help the overlord fight on the field of honour, but also serve as his eyes and ears among the dissenting nobility beneath him, assuming there is any, or assuming that his courtiers aren't in on the coup.
For 20 points you could call your Overlord the king of kings of his Dynasty, and give him and whatever unit he joins Relentless. Yay.
This option was removed in the 7th Ed codex, which really don't matter, since nobody used the option anyway, but Phaerons are still in the fluff, and you can call your Overlord a Phaeron if you so desire.
And get the relentless anyway from having a Reclamation legion around.
Toys and Tricks
You don't get much out of your Overlord on the tabletop without any upgrades. S/T5, kinda like the Regular Lord, but has WS/BS 5, an extra attack and 3 wounds. Slap on 60 more points and he trades in that 3+ save for a 2+/4++. 20 more swaps the Staff of Light for a Warscythe. 25 points each on top of that gives him a Res Orb of his very own, and a Tachyon Arrow, which is a one-use, 120" Hammerhead shot. For 10 more points he can have a cluster of Mindshackle Scarabs, which can lower the WS of an enemy model if they fail a Fear test on 3D6, and you can buy a Phylactery for 15 points to give him It Will Not Die. Do a little math and that makes that 80 point piece a 235 point ruiner-of-days. Pick and choose the toys you need from mission to mission, you will rarely ever need all of them in the same match.
The Royal Court
It comes highly recommended that you load up your Overlord with a Royal Court if you are playing the Necron Decurion Detatchment. Up to 3 each of Necron Lords however you like them, and 3 Crypteks. Be warned, Royal Courts can get expensive fast, so be sure you will actually use all the tricks you pay for, and make sure you make the Overlord in the Royal Court your Warlord, which gives you a reroll on the Warlord traits table.
Catacomb Command Barge
For only 55 points more, there is no reason not to use this magnificent bastard boat. It's a chariot that comes with an underslung Tesla or Gauss Cannon and has the Quantum shielding special rule, so its mediocre AV 11 gets buffed to 13 on the front and sides until you penetrate it once. Unless you really want to give him a Res Orb and have him slog it with some Troops or Lychguards, the bastard boat is the way to go. Throw a Phylactery on the Overlord and both him AND the banana boat get It Will Not Die. Throw a Phase Shifter on him as well, and you can allocate wounds that would normally penetrate the barge (read melta) on him and take the 4++ save instead. And if you're feeling particularly froggy, you can put a wound on the Overlord to repair a hull point off the pimp boat or treat "weapon destroyed" as "crew stunned".
UPDATE!!! Thanks to the 7th Edition rules, this bastard boat can only taken by Overlords (7th Ed. FAQ); However you can now treat 'weapons destroyed' as 'crew stunned', can choose to allocate hits to either the barge or the Overlord (your choice) and should the Overlord perish and pass his Reanimation Protocols then the Barge also comes back with 1 hullpoint!
- Imotekh the Stormlord - Particularly ego-maniacal. He woke up during the infighting that had ensued between the other Overlords after the old king had kicked the bucket. He decided that he had been Nemesor for too long and needed to change up, kicked the other Overlords asses and crowned himself Phaeron.
- Nemesor Zahndrekh - A crazy old man who thinks he and his Court are still flesh and blood. He also sees everyone as Necrontyr, even his enemies. Noted for having dinner served every night, even though no one, not even he, eats anything.
- Trazyn the Infinite - A HI-larious combination of thieving bastard and historical preservationist. Among his collection are:
- Sebastian Thor's head (or one of the many fakes scattered around the universe; hard to tell with Thor)
- An ossified Enslaver
- A frozen man in baroque power armor (who is totally not a lost Primarch).
- Creed. Yes, that Creed.
- A perfect clone of Fulgrim (that hasn't yet been corrupted by Chaos).
- And a nice life-size diorama of five full regiments of Catachan Jungle Fighters.
- Anrakyr the Traveller - Instead of letting himself become embroiled in politics, he forsook his rule of the Tomb World Pyrrhia to roam the stars helping other Tombs awaken safely, and all he "asks" in return is a tithe of soldiers and supplies that he may continue his work. He upgrades 1 unit of Immortals in your army to Pyrrhian Eternals, giving them Furious Charge and Counter-Attack. He can also possess enemy vehicles and have them shoot at their own allies.