/jp/ - Otaku Culture

>>16719785

The 助動詞 き is the 過去形 form in 古文, and し is its corresponding 連体形. It attaches to the 連用形 (pre-masu stem) of a verb , i.e. 裂き in your picture. は is just normal は. See an example of how this formation works in an excerpt from 舞姫 by 森鴎外 (1890) in the original 古文 and then a modern translation.

>余が車を下りしは「カイゼルホオフ」の入口なり。
>私が馬車を下りたのはカイザーホーフ・ホテルの入り口だった。

So for an awkward translation of your pic in the same sort of vein:
>What hath rent the shroud of night is the fang of insurrection that has attained a new power!
In other words standard chuuni stuff.

Source: 1 hour googling, 10+ years of experience as professional googler