Fhyujk

I am a new GM and new to D&D. Currently, I am running the Lost Mines of Phandelver (LMoP) D&D 5e starter campaign. My group have just finished the Cragmaw Hideout section, but as we ran it we came across some situations that I was not sure how to handle.

Specifically, at a certain point the party encountered three goblins in a cave with a waterfall (area 7 "Twin pools cave" within Cragmaw Hideout). In the description of the area the book suggests that, when they spot the party, one of the goblins moves to next room (area 8 "Klarg's Cave") to warn his allies that there are intruders.

The party killed the two remaining goblins in area 7 and then moved into area 8. My questions have to do with the characters transition from one room to the other:

1. Is it reasonable that the warned enemies (who are hiding behind stalagmites and crates) attack the group immediately when the group enters the room (like taking the Ready action from the previous round with the condition "I attack any enemy appears at the entrance of the room")?




2. Is it better to start a new round every time the party enters to a new room/cave, even though a PC may have enough speed to cross a certain distance in the previous cave, and then enter the new one (in the same round)? If this is reasonable the PCs would have the chance (given that their initiative is greater than that of enemies) to use their Wisdom (Perception) as an action (assuming that the Dexterity(Hide) check score of enemies is above players passive perception) and avoid being surprised.

Unless I am missing something in your scenario, it seems like the "surprise" mechanic would fit perfect here:

A band of adventurers sneaks up on a bandit camp, springing from the trees to attack them. A gelatinous cube glides down a dungeon passage, unnoticed by the adventurers until the cube engulfs one of them. In these situations, one side of the battle gains surprise over the other.

The GM determines who might be surprised. If neither side tries to be stealthy, they automatically notice each other. Otherwise, the GM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (Perception) score of each creature on the opposing side. Any character or monster that doesn't notice a threat is surprised at the start of the encounter.

If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends. A member of a group can be surprised even if the other members aren't.

Since the goblins are attempting to be stealthy, this mechanic would apply, even though the party members may be aware the goblins are waiting for them (you could impose disadvantage on the goblins' stealth checks in this case).

Is it better to start a new round every time the party enters to a new room/cave, even though a PC may have enough speed to cross a certain distance in the previous cave, and then enter the new one (in the same round)?

Unless the PCs are continuing to actively pursue specific enemies between rooms/caves (thus continuing a combat encounter), you should be starting a new combat encounter upon entering a room, not a new round. From your description of the scenario, it sounds like the goblins are simply waiting in room 8 for the party, and all the goblins involved in the combat encounter in room 7 were slain, meaning that room 7's combat encounter has finished (despite the warned goblins being aware of the PCs), and a new encounter would begin when the goblins in room 8 attempted to surprise the PCs upon their entry.