邂逅せし瘴炎 what does the せし part mean?


I found that title in the Monster Hunter game and it was translated as "A
Meeting with Blazing Miasma", but what does せし mean there? It kind of sounds
that it might be a case of classical Japanese grammar there, I think. I didn't
find anything that could help me, so, can someone tell what it means? I think
it must give some sort of nuance.




In modern Japanese, 邂逅 is a する-verb (which are also known as サ変), but in
classical-esque Japanese the する becomes す (see 愛する vs 愛す etc). The し comes
from the 連体形 (form used to connect to nouns such as 瘴炎) of the auxiliary
particle [**き**](https://kobun.weblio.jp/content/%E3%81%8D), which is a
particle that is well known for having crazy conjugation patterns. き is used
similarly to how **た** is used in modern Japanese to indicate things that
happened in the past. Its supposedly unique point is that it's the past that
one has experienced personally.

Now in classical Japanese the verb ending す's 連用形 (form used to connect to
non-nouns) is し so you might expect the correct conjugation to be 邂逅しし.
However, き with all of its odd conjugations has a special rule where if it
connects in the 連体形 to a サ変 verb, the サ変 verb instead connects in the 未然形,
which is **せ**. That is why it is used as **せし**

Here is the progression:

> 邂逅す＋き＋瘴炎
>
> 邂逅せ＋し＋瘴炎
>
> 邂逅せし瘴炎

Here's a diagram of some of the crazy rules of the ultra special conjugations
of き. It's しき, but also せし and せしか. [![enter image description
here](https://i.stack.imgur.com/ZvTI3.png)](https://i.stack.imgur.com/ZvTI3.png)

I got the image from [this page about き and the related
けり](https://www.kotenbunpou.com/%E5%8A%A9%E5%8B%95%E8%A9%9E/%E3%81%8D-%E3%81%91%E3%82%8A/)
(the past that one knows about through hearsay).




In modern Japanese, 邂逅 is a する-verb (which are also known as サ変), but in
classical-esque Japanese the する becomes す (see 愛する vs 愛す etc). The し comes
from the 連体形 (form used to connect to nouns such as 瘴炎) of the auxiliary
particle [**き**](https://kobun.weblio.jp/content/%E3%81%8D), which is a
particle that is well known for having crazy conjugation patterns. き is used
similarly to how **た** is used in modern Japanese to indicate things that
happened in the past. Its supposedly unique point is that it's the past that
one has experienced personally.

Now in classical Japanese the verb ending す's 連用形 (form used to connect to
non-nouns) is し so you might expect the correct conjugation to be 邂逅しし.
However, き with all of its odd conjugations has a special rule where if it
connects in the 連体形 to a サ変 verb, the サ変 verb instead connects in the 未然形,
which is **せ**. That is why it is used as **せし**

Here is the progression:

> 邂逅す＋き＋瘴炎
>
> 邂逅せ＋し＋瘴炎
>
> 邂逅せし瘴炎

Here's a diagram of some of the crazy rules of the ultra special conjugations
of き. It's しき, but also せし and せしか. [![enter image description
here](https://i.stack.imgur.com/ZvTI3.png)](https://i.stack.imgur.com/ZvTI3.png)

I got the image from [this page about き and the related
けり](https://www.kotenbunpou.com/%E5%8A%A9%E5%8B%95%E8%A9%9E/%E3%81%8D-%E3%81%91%E3%82%8A/)
(the past that one knows about through hearsay).

