There is nothing on the inside of the ring, save for a little tarnishing. 

Milamber casts Firebolt at the altar to see if it reacts in any way. He is hoping it is mundane but knowing it was used for more nefarious purposes he decides to test it anyway. Attack: 6 Damage: 13

OOC: oops

The firebolt splashes against the stone of the altar and fizzles out without any apparently reaction.

"Alright, let's clear this place out so they can rest in peace." Rosa turns and goes back to the other room. He'll see people at the altar, so he'll walk around to the trash pile to make sure nothing's in it.

Grythel let the ring on the hand of the skeleton again. It's gorss but he doesnt0 want naything from the dead, and specially from this house. 

He then goes back with Rosa and follows him

"Nothing that could help us I am afraid.." he says to him.

(Rosa is a boy)

Rosa will continue into the room, and look over the trash pile to see what's in it. 

Investigation 4

(Whew he does NOT notice anything)

Rosa, how are you inspecting the trash pile? Are you just walking around or digging into the muck?

Milamber, seeing that his firebolt had no effect decides to try one last thing and pulling a gold coin from his belt he sets it on the altar and watches for any arcane response to the "sacrifice." 

Arcana: 20

(With a roll like that, he's probably poking it with his sword) 

Rosa walks around the pile, occasionally jabbing it with his sword slightly to see if anything pops out.

Milamber places the coin on the altar and nothing happens. However, as Rosa stabs into the pile of refuse, it shudders and shifts, rising up from the water, sending a smell of rotting plant matter across Rosa's face! Anyone on the dais is 20-25 feet from the creature, the furthest away would be the corners of the room which are about 40 feet from the creature.

COMBAT! Bold below may act:
Rosamund Carpenter
Muirdan
Grythek
Tengen
Milamber
Creature

"Oh, by all the hells what did you do that for!" Tengen calls out as she summons a golden globe of light around her hand and launches it at the disgusting creature. She then moved to position herself on the other side of the alter behind the dais from the creature.

Casts Guiding Bolt

Attack 23

Damage 12 radiant damage, if hits and next attack has advantage. 

Tengen's magic slams into the creature, outlining it in a faint glow! The next attack has advantage against the creature.

Milamber moves his hands in a swirling motion creating a ball of flame with an oscillating spectrum of colors and with a throwing motion sends it at the creature.

Casts: Chromatic Orb with fire damage selected

Attack: 19 Damage: 22

“What’s that?!” Ask Grythek jumping to fight alongside his friends, trying to attack from another direction to keep the thing unbalanced. 

Attack: 18 Damage: 10

Attack: 20 Damage: 11

Muirdan, seeing something seemingly-not-undead opposing them, charges the creature and swings at it with his warhammer.

Hammer: 9 Damage: 10

Rosa just looks at the creature for a long second before his face contorts with anger and he shouts, “I hate this house!”

(bonus action rage)

Attack 11 Damage 11

(Bump)

(OOC: Grythek, what's the second attack coming from, out of curiosity)

As a well oiled unit, you all spring into action, everyone save for Rosa managing to land solid strikes against the creature. Milamber, it seems like the fire didn't do nearly as much to the creature as you would have expected. All told, the creature doesn't look that much worse for wear after the assault however, as it's writhing mass shifts as if surveying you. The pile of animated plant matter spies the dwarf and lashes out with a pair of heavy vines!

Attack on Muirdan: 27 for 24 bludgeoning damage.
Attack on Muirdan: 17 for 14 bludgeoning damage.

If both attacks hit, you are grappled and need to make a DC14 Athletics or Acrobatics check to escape on your turn.

COMBAT! Bold below may act:
Rosamund Carpenter
Muirdan
Grythek
Tengen
Milamber
Creature

Milamber Grumbles at the seeming fire resistance of the beast and then decides. If fire does not hurt it as well, perhaps the opposite would work better. A blue ball forms in Milambers hand and once again he flings a bolt of energy at the monster. The ray of frost flies across the room towards it. Attack: 18 Damage: 8