Royal Wardens possess the initiative to adapt on the battlefield and can modify the orders to phalanxes of Necron Infantry. While they retain an independence of thought, their command protocols still make them unquestionably loyal. Royal Wardens are armed with Relic Gauss Blasters. Despite their formidable combat prowess, however, Royal Wardens also have direct influence over his underlings due to his close connection with his Lord. This makes him just as much as an adept commander as he is, a warrior.
At last, the Necrons have their own Primaris Lieutenant. He is a support character with a relic gauss blaster (Rapid Fire 2 and D2 compared to the base Immortal). His Relentless March grants a <DYNASTY> CORE unit +1 to its Move characteristic. During the command phase, he can let a <DYNASTY> CORE unit within 9" fall back and remain able to shoot and charge. This can seriously boost the effectiveness of a large blob of Warriors or Immortals; while they have a Royal Warden nearby, their relatively-short-ranged shooting can't be turned off simply by being charged.
If you're a Mephrit boy, you gain the Conduit of Stars relic. This is a direct upgrade for the Royal Wardens' gun with +1 strength +6” range and +1 base shot. (S5 AP-2 d2, rapid fire 2, 30” —> S6 AP-2, d2, rapid fire 3, 36”). Voltaic Staff is often a better upgrade but there is the meme of getting 6 shots instead of 2 at 15-18 inches.