Well, no monster is imminently lunging toward him so this is arguably an improvement, albeit one that came about via a monster succeeding at doing just that.

He casts Light on his holy symbol, shines it around in the shadowy corners of the chamber, tries to guess the distance to the hole in the roof, and finally takes the corridor out.

There's a doorframe. Big and imposing. Behind it, a patch of green amid darkness.

Huh. Is there another roof hole? He steps closer to check.

Suddenly, a very large flower with a powder-white face pops up from under the green patch! To someone with Chelish levels of face-reading, he looks quite confused and less than sincere, but he's doing a passable job at 'friendliness' nevertheless.

"Howdy! I'm... me, Flowey the Flower. And aren't you interesting!"

It's definitely not Taldane or Infernal. Somehow, it's understandable anyway.

...that's not how Tongues works but maybe it's how the - no, truespeech works like Tongues, actually, as far as he knows? Huh.

If he tries to say "pardon me" does it come out in the new language too?

It does, though it's also understandable to Blai.

There's probably some global spell about language in the Underground.

There's probably lots of global spells about various things in the Underground.

Undertale is not the kind of game to pretend logistics don't exist, but more than that, it's definitely not the kind of game to actually delve into them.

"No worries! We're all friends here, hee hee hee."

"Say, how'd you even fall down here? The hole up there isn't wide enough for an old man."

Probably Blai is the one subject to Tongues. He isn't sure when or how that happened, which is concerning, but he can't detect at this time any other effects on him and doesn't have a supervisor to go to with the security issue. Except Iomedae, of course; quick sitrep prayer for Her.

"I don't think I fell. I was attacked by some kind of snake monster I didn't recognize and then I was there. I'm Select Blai Artigas."

"Were you now. How very interesting. Now what if you told me the truth instead? I hear lying isn't very nice."

"It's also against my religion. I acknowledge it's an unusual story and perhaps it sounds even moreso to you than to me."

There's unsuppressed rage on the flower's face, now, contorted into something quite unsightly.

"Mm. You know, even an IDIOT would know that there's no monsters up on the Surface. SO WHO DO YOU TAKE ME FOR, THEN?"

A dense ring of petal-like magical projectiles surrounds Blai. They track his motions perfectly and slowly, gradually contract.

"What is it, really? Tell me, or DIE."

"Qualm!" exclaims Blai.

Qualm

[...]

Saving Throw Will negates

You know, this might do something against someone that isn't a bunch of centuries-old plant matter animated entirely by literal liquid determination.

LOL.

You get hit for a bunch.

Huh, that didn't do much damage at all.

You get hit for way more, then, in quite a bit less than 6 seconds! And then, you-

OW! Ouch ow owchie!

And then the plant thing is hit by a miniature Fireball. Which doesn't explode or burn him, but does uproot and bounce him way off into the darkness.

And nearly simultaneously, Blai is instantly healed.

"What a terrible creature, torturing such a fine young man! Ah, do not be afraid, my child. I am Toriel, caretaker of the ruins."

What kind of an instruction is "do not be afraid".

"Hello," says Blai.

It's a very normal instruction for very normal people that might be scared by a sudden exchange of spells even when nothing is to be afraid of, silly!

"I pass through here every day to see if anyone has fallen down. You are the first human to come here in a long time."

"I will do my best to protect you during your time here. Come! I shall guide you through the catacombs."

Toriel is sincere, or much better at concealing emotions than Flowey was, or doesn't have natural humanlike emotional expression to begin with now that we've raised the topic anyway.

"Could you perhaps tell me where I am."

"We are in the Underground. Specifically, the upper reaches of The Ruins."

"What continent is this underneath?"

"Hmm. Truthfully, I do not remember. I believe we happen to lie under a nation currently called America, but- huh."

"Shouldn't you know which continent your home is at? That you don't implies a considerable failure of education, if you ask me."

"I didn't fall. I was attacked by some kind of snake monster and this somehow sent me there, through that hall." Point. "I don't know of a place called America. At the time I was attacked I was in Cheliax in the archduchy of Menador."

"Truthfully, I find it rather hard to believe you have encountered a monster outside of the Barrier, much less one that would send you, of all places, to this exact place. Still, we don't need to jump to conclusions, especially on something with little expedience or confidence. Perhaps you know something I don't, young one."

"I do not recognize any of these place names either. Not particularly surprising, perhaps, since we've been totally cut off from the Surface for quite some centuries."