I'm going to start with general comments, then get into specific nitpicks below.
First off, and most importantly, this lacks a hook. It's a weird liquid that controls people, that's about it. Sure it's an ice cube, but you don't actually do a whole lot with that theme. You need a story, or some interesting horror, something to grab the reader and make them want to keep reading. This idea is a no-go if you can't find a more interesting and unique hook than "an ice cube that controls people".
Beyond that, you've got some content issues. The containment procedures don't really make sense (details below), and you never really address its sentience. It's apparently alive, and can control people, but…why? What does it want? How smart is it? What are its motives?
Another thing: I'm not sure where the site as a whole stands on this, but personally I dislike SCPs which require other SCPs to contain. It's okay to invent fictional technology to contain stuff, within reason (see the "Scranton Reality Anchors" used in a couple SCPs), but I don't like if I have to read an entirely different article to understand why something is contained the way it is.
That's it for broad strokes, let's get into some specific nitpicks:
should this temperature ever change the immediate room is to be evacuated
Why would there ever be people in the room to begin with? At -50C, you'd need serious gear to not succumb to hypothermia in minutes.
SCP-0707 will melt into what appears to be a puddle of a [DATA EXPUNGED] acid
Couple things here:
- Generally you use [REDACTED] to cover one or two words, and [DATA EXPUNGED] to cover a whole sentence or paragraph. Here you'd probably use REDACTED.
- Why is only the type of acid redacted, but not the fact that it's acid?
- Why does it "appear" to be this type of acid? What evidence do we have that it is?
If you're not confident with the chemistry knowledge, you can just say "will melt into an unknown clear, viscous substance that testing indicates is highly acidic" or something.
SCP-0707-1 remains alive during this process, until either SCP-0707 relinquishes control of SCP-0707-1, or SCP-0707-1 is killed in some way.
What happens to someone controlled after being released? Are they fine? Are they covered in acid burns?
SCP-0707, when exposed to any temperature higher than -50 degrees Celsius, has been seen to expand itself up to a large cube 10m x 10m x 10m
If it only expands to 10x10x10, why is that the exact dimensions of the containment chamber? Why not just ignore the temperature and build a chamber that's 11x11x11, then downgrade the thing to "safe"?
There's a couple other little nitpicks with tone, word choice, and phrasing, but those are comparatively minor; for now I'd focus on finding a better hook (or an entirely new idea with a good hook) and on improving the containment procedures.
P.S. You should be using the SCP Sandbox Site for drafts, not pastebin; it has the exact same formatting as the wiki itself so everything is much easier to read and proofreaders can catch formatting issues as well. Also, just as a general Best Practice, you should use a placeholder number for your SCP (most just use "SCP-XXXX").
