D&D 5E 5e Rules for creatures occupying the same space?

[Stormrazor2000]

My apologies if this has been covered before but I've checked the rule books and tried the search function to no avail.

I'm looking for rules for how to handle the situation when a monster can occupy the same space as a character. Examples being things like swarms, water elementals and the like. Can those monsters be targeted normally with no danger to the PC in that same space?

Here is an example that came up in a recent game. A fighter enters a room and is engulfed by a swarm of insects. The nasty little buggers are crawling all over him (occupying his space). The ranger wants to attack the swarm with an arrow. The question arises - can she attack the swarm normally as if the swarm was in it's own space? Or does the swarm get some sort of cover? Is the attack at disadvantage as she tries not to hit the fighter? Or perhaps is the attack made as normal but some of the damage done to the swarm also get applied to the fighter?

 

[EvanNave55]

I doubt there would be any official rules for something like this in 5e with how rules sparse (ahem) light it is. They would just leave it up to the dm so probably something like disadvantage, or maybe hlaf the damage dealt to the swarm is dealt to the player as well.

 

[epithet]

Use the rule in the DMG (page 272) for taking cover behind another creature. The swarm takes cover behind the the Fighter, and gets a +5 bonus to its armor class. If the attack hits, apply the damage to the swarm (the swarm has resistance to piercing damage, right?) If the attack misses, compare the attack roll to the Fighter's armor class. If would hit, apply the damage to the Fighter normally.

 

[Stormrazor2000]

Thanks for the input!

 

[Tormyr]

There are probably several ways to rule attacking a swarm in another creature's space. Every published swarm has a 0 ft. reach and attacks a creature that shares its space.

So if a creature attacks a swarm that is sharing a space with another creature how does that resolve? I can think of a few options:
1. If the attacker hits the swarm, it does damage half damage to the other creature.
2. Resolve the attack roll against both the swarm and the creature.
3. Same as #2 but give the other creature a +2 to AC for half cover from the swarm.
4. Only have the attack roll to hit the swarm.

Personally, I would probably choose 2 or 3, but it depends on the situation.

This is only for attack rolls. Area of Effect spells like fireball already target everyone in the space.

 

[DMCF]

A swarm that looses half it's HP can't regenerate it's hp as much of the swarm is presumably dead. I'd suggest that a swarm could only be occupied at this point since it has diminished in size.

 

[Arial Black]

If I was covered by an angry swarm of bees, and my friend says, "Don't worry! I'll shoot arrows at the bees...!"