OOC: If Skalisss took the free save attempt given by Vlastos' Heal check, he'd have stayed at 15 HP by my count and not taken further damage.
Also, just to be clear about it, here's what Latanos said:
"(W)e don't take kindly to necromancers. Even after they themselves have passed on, there are rites we undertake to make a reckoning for their actions. My research has uncovered the final resting place of a necromancer that was of particular note a century ago. He and his undead terrorized Marlowe's Grove, a village in the Starkreach Woods, until it was abandoned. When his time came, Skelleks, the necromancer who tormented Marlowe's Grove, chose to place his tomb in the graveyard of Marlowe's Grove, amongst many of those who fell to his undead horrors."
"I want you to go to Marlowe's Grove, find Skelleks' tomb, and return with his skull. ... Further, my research indicates that, while most of Skelleks' worldly goods were passed on to his apprentice - who my order has already... taken care of - some trophies of Skelleks' vanquished foes are interned with him in the tomb. These items would be yours, should you find them. The skull only do I require."
In other words, the necromancer is long dead. The tomb is, as far as Latanos knows, a tomb, and not the secret lair of an active necromancer. So take that into consideration when deciding to press on or not.
Also, dusk fell as the fight started. One more piece of info to weigh.
So, press on, or rest for the night?