I’d hope to reply to these earlier, but I’ve been busy readying for relatives to visit next week.
In the prior panel, there is talk about how the four were reborn to seek out and protect Endymion, but their memories did not return to them..
Looking at the whole of the panel in question, we have:
「またしても
あいつの
手のうちに
はまり
この身を
売った」
I know you’re asking about the last word, but I’ll go word by word.
またしても has the meaning of something repeating, of it happening again. On the prior page, it was shown that the four turned against Endymion, as they joined forces with Beryl who was controlled by the evil entity.
あいつ refers to the evil entity. (I forget if the entity’s name has used yet. I think Beryl mentioned it in an earlier chapter, but I could be wrong, so I’m simply referring to Metalia not by name here)
手のうち can mean “(under one’s) control”.
はまり means “to fall into” (such as falling into a trap, or being deceived). Or in this case, pulling it all together, “Once again we fell into their control.”
From there:
「この身を売った」
Going backwards, 売った here is indeed sold, like to give away something in exchange for another thing. Another English word for “sold” here would be “traded” or “exchanged”.
The item they sold is marked by を, as it is the object of the verb. 「この身」 here means “my body”, but I think in this case it’s more like “our bodies” as it’s referring to the four of them. (If anyone reads this otherwise, don’t hesitate to say so!) In English, I would possible write this as “we sold ourselves” kind of like the expression “sell your soul to the devil”. They traded their bodies to the entity controlling Beryl.
There’s definitely a lot going on in Act 9! Coming off of the cliffhanger from the last chapter, you get a big info dump on the past in the form of memories/flashbacks happening interviewed with the present, and the pacing feels all over the place and it ends with a haircut and group chat in Usagi’s room. (I’m not complaining, but definitely acknowledging.)