Help a GM out with this scenario

[Atalius]

My players are level 6 currently in my homebrew campaign. One of my players wishes to enter into a room full of monsters as a wild shaped rat and then proceed to cast spells like flurry of Snowballs, flaming sphere etc without being noticed. Any suggestions on how I should play this? Would it be reasonable that non of the monsters know the rat is casting spells? Or does the rat make gestures when casting spells with somatic components?

[Dajur]

He will definitely be noticed. Right away. Not only do spells require verbal, somatic and/or physical components, spells actually radiate power. All spells coming from the caster have physical manifestations that are easily traced back to the caster, no matter what their current shape.

[Fuzzy-Wuzzy]

As Dajur says. Relevant FAQ.

[Slim Jim]

If the monsters are relatively brainless, they're not going to know the difference between magic and an actual hailstorm or wildfire. Sufficiently hungry and quick of snout, they might brave the elements to wolf down a tasty morsel scurrying underfoot. If they are intelligent, they will straight up murder the first thing they see moving that isn't one of them.

[Atalius]

Ahh I see, would he be able to scout a room as a rat and then casually walk back out if the room? I don't see why monsters would start chasing a rat around a room?

[Fuzzy-Wuzzy]

Atalius wrote:

Ahh I see, would he be able to scout a room as a rat and then casually walk back out if the room?

Sure, classic tactic.

Atalius wrote:

I don't see why monsters would start chasing a rat around a room?

Depends how hungry the monsters are, really. He definitely wants to make a Stealth attempt.

[Shiroi]

Yeah, stealth in and hope nothing inside is even remotely intelligent. If the monsters don't have int of 3+, I'd say they might be panicked and may or may not try to attack the rat. On the other hand, they might well bust down the door and trample the rest of the party in such a state. This is also a major expenditure of resources for the player, so some small reward may be in order but if he trivializes the entire encounter with this tactic it should probably cost him hard later when he's in another fight and out of spells.