Part 3: Investigating the Moathouse Ruins
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Alice lets the light from her torch illuminate the small 10' x 15' room. By the appearance of the chamber, this place was once the domicile of someone of importance, but is now stripped of everything save broken and ruined furnishings. However, her torchlight catches a gleam directly next her on the right as she peers inside. One wall cresset remains near the outer wall, and its nondescript torch stub is a silver baton, probably worth some gold.
Seeing nothing else of interest in the room, and most importantly no hostiles, Alice exits the room and opens the door at the west end of the hallway...

Alice opens the door to the far west, at the end of the hallway. This room, like many of the others room built directly inside the moathouse walls, has arrow slits for archers to use when the castle is under siege, which allow a degree of sunlight to enter and render torches unnecessary during the daylight.
But before she has a chance to examine the room in any degree of detail a sense of immediate danger accompanied a swift movement from the right side of the room along with a barely perceptible slapping of feet on stone, then a 5' long, giant lizard is on Alice, whereby it delivers a vicious bite at the cleric. Fortunately, the lizard approaches for a bad angle and it's shoulder collides against the door frame first, bringing it short of its target as its jaws snap shut a fiit from Alice's face.
Turn order is as follows:
-->1. Gilly (8)
2. Alice (6)
3. Eltrezar (5)
4. Angel (4)
5. Giant Lizard (1)
6. Elmo (6, 2-handed)
The Giant Lizard attacked at a diagonal angle. The door is in the middle of the hallway, so if anyone wishes to rush into the room on their turn they can enter through L12 or L13, as both spaces contain the door. Remember, you can pass through a fellow PCs space when you move, but you may not stop on a fellow PC's space, and you may not pass through an enemy's space.
@KCC69: This Giant Lizard is large for a lizard, but at 5' in length, it's not greater than human-sized. So Gilly's AC for this encounter is 4.
Rolls
Party Surprise roll - (1d6)
Giant Lizard Attack roll, Damage roll - (1d20, 1d8)
1d20 : (5) = 5
1d8 : (4) = 4
Angel Initiative roll - (1d6+1)
(3) + 1 = 4
Gilly Initiative roll - (1d6+2)
(6) + 2 = 8
Alice Initiative roll - (1d6+1)
(5) + 1 = 6
Eltrezar Initiative roll - (1d6-1)
(6) - 1 = 5
Elmo Initiative roll - (1d6+2)
(4) + 2 = 6
Giant Lizard Initiative roll - (1d6)
(1) = 1
Rolls
Attack - (1d20+1)
(13) + 1 = 14
Damage - (1d6+1)
(1) + 1 = 2
Rolls
Attack - (1d20+1)
(3) + 1 = 4
Damage - (1d6+1)
(6) + 1 = 7
Alice charges into the room as well and attack from the reptile's other diagonal rear, but it flinches at Gilly's stab and Alice's hammer whiffs through the air.

1. Gilly (8)
2. Alice (6)
-->3. Eltrezar (5)
4. Angel (4)
5. Giant Lizard (1)
6. Elmo (6, 2-handed)
Rolls
Magic Missile - (1d6+1)
(1) + 1 = 2
I could make the argument that Eltrezar would have to declare he's casting a spell at the beginning of the round, but I think that's going to be a difficult rule to enforce in a PbP game to be honest, because it's going to require every player to sit and wait for a magic casters to declare before the game can resume each round.
However, I would be willing to argue that a caster has to see their target to use Magic Missile, and it would be pretty difficult for Eltrezar to see the lizard considering where the lizard is standing in relation to where the actual door is, and therefore Magic Missile might not be possible.

So I'll give you two options:
1) You can keep the roll as is, doing the 2 damage, and use up your spell slot.
or
2) You can assume that Magic Missile wouldn't work right now, and retcon your turn this round.
I'm fine with either, BUT if you retcon the turn and move to a place where you have a better line of sight and cast Magic Missile this round, you have to stick with the "1" roll. If you opt to retcon the Magic Missile attack this round altogether, you can do something else instead, such as move and dagger, move in the room but stay away and let the less squishy PCs handle the melee, etc.
Rolls
Attack - (1d20)
(8) = 8
Damage - (1d4)
(4) = 4

1. Gilly (8)
2. Alice (6)
3. Eltrezar (5)
4. --> Angel (4)
5. Giant Lizard (1)
6. Elmo (6, 2-handed)
...Unfortunately the arrow bounces off the wall behind it and lands near Eltrezar's dagger.
The lizard turns and snaps at the attackers behind it...
...Targeting Gilly, it's thick jaws slam shut just in front of her face as she instinctively pulls her head back and she realizes just how lethal a single bite could be.
Elmo rushes in then and swings his battle axe at the big reptile...
...which deftly slams against the lizard's skull.
Rolls
Angel Attack roll, Damage roll - (1d20+2, 1d6)
1d20+2 : (6) + 2 = 8
1d6 : (2) = 2
Giant Lizard target selection (1-3: Alice, 4-6: Gilly) - (1d6)
(6) = 6
Giant Lizard Attack roll, Damage roll - (1d20, 1d8)
1d20 : (3) = 3
1d8 : (5) = 5
Elmo Attack roll, Damage roll - (1d20+4, 1d6+2)
1d20+4 : (19) + 4 = 23
1d6+2 : (1) + 2 = 3
-->1. Gilly (6)
2. Eltrezar, Giant Lizard (4)
3. Angel (3)
4. Alice (2)
5. Elmo (3, 2-handed)

Rolls
Angel Initiative roll - (1d6+1)
(2) + 1 = 3
Gilly Initiative roll - (1d6+2)
(4) + 2 = 6
Alice Initiative roll - (1d6+1)
(1) + 1 = 2
Eltrezar Initiative roll - (1d6-1)
(5) - 1 = 4
Elmo Initiative roll - (1d6+2)
(1) + 2 = 3
Giant Lizard Initiative roll - (1d6)
(4) = 4
"Gilly keep back and pepper the beast with arrows! Let's see if this monster can bite through my steel!"