On Saturday, I battled mech IG with my Necrons.
Necrons:
Overlord w/ warscythe, CBB
DLord w/ weave
5 Praetorians
2x 10 Immortals w/ NS
10 Warriors w/ NS
3 Canoptek Spyders
2x Annihilation Barge
IG:
Primaris Psyker
10 Veterans on foot
30 Vets w/ Chimera
2x Hellhound
3 Hellhounds w/ mulitlaser
2x Leman Russ
1 Hydra
Mission: killpoints.
Deployment: the diagonal one
IG was setting up first with a large power blob in the centre. Necrons deployed in the centre behind a larger ruin giving partial cover but as close as possible to the enemy.
IG had first turn. No night fight. My DLord attached to the Praetorians got their attention as it was the closest model of the unit. After failing two saves and another LoS (from a lascannon), he died. Moreover, one Praetorian died from a LR battle shell. Not other casualties.
Necrons moved forward. The Overloard zoomed down 30'' close to the centrally deployed Leman Russ. The Overlord had to spend one wound to save an immobilized result. Barges downed one Chimera.
IG moved one Hellhound and one Chimera closer to my front ranks, able to target my Spyder. One wound only. IG was unable to down the CCB as it had a 4+ cover save after going flat out. Deep striking Vets got delayed.
Now the Spyders destroyed the Hellhound and the Chimeras close to it was downed by tesla. The passengers got decimated by the arriving Immortals (deployed from a NS). Praetorians destroyed one Chimera parked in front of the power blob. The Overlord vector striked leaving a wrack (LR) back. IG already started to crumble.
Next, the power blob destroyed the Praetorians left blank in front of them. Vets came from reserve dowing the CCB with a melta shot. IG managed to kill the whole Immortals squad so that no one could come back.
Necrons still moved forward. The Overlord charged the Vets challenged the leader killing him. Later the Vets fell back and got destroyed. Warriors popped the Hydra after being deployed from the NS. Later on, the Warriors got charged by outflanking Sentinals. Funny to see that they killed the Sentinals in cc, 3+ to hit, 6+ to strip off one hull point. The Warriors were left untouched.
As said, IG crumbled and at the end had just a few soldiers from the power blob and one LR intact, while Necrons only lost CCB, one Immortal squad, DLord, and Praetorians.
Summing up, Necrons also work without Wraiths. Two Overlords in CCBs seem to work. Zoom them down in round one, and with a 4+ cover save they might survive enemy shooting. Next turn, they could cause havoc. This would give the rest of the army time to get into position.
