The Named Monsters were dead, and it was impossible for Draco not to know.
Though Keldars didn't receive notifications when a Named Monster was killed, these monsters were all intelligent.
It was highly likely they had sent warnings to Draco during their last moments, and their death cries were loud enough to alert anyone nearby.
According to what Arlon remembered from the past timeline, Draco's lair was beneath the mansion.
With the Named Monsters gone, the remaining Keldar forces in the mansion were in disarray. They posed no real threat to Arlon and his copy now that both were level 100.
The duo moved silently through the dark halls, dispatching the lesser Keldars with practiced efficiency.
Arlon used his Detection spell periodically, sweeping for signs of Draco, but the Dragon-like Keldar remained elusive.