Immortal Mantis (75% off)

"there is not even a site with a review of this game on the net"

Well, there's actually this one thing.. It's not quite a review, persay, but..

https://itch.io/t/2079615/immortal-mantis

While I can't find any supporting data to make this anything more than an assumption based on the information present on the linked page, the implied situation isn't exactly great: Going off what's indicated there, apparently the game was posted to itch.io, then the game was removed and the developer's account was suspended because the game was carrying a trojan.

While a small portion of those Steam reviews do look kind of sketchy, there doesn't seem to be any similar indication of malware off the current Steam reviews, and Steam does thoroughly virus scan anything uploaded to it. All the same, it feels like it'd be better to put off promoting this game on SG until it gets a bit more robust of a validation on being safe to purchase.

Given how mixed some of the details in the reviews are, it might also be worth waiting until the game has more reviews simply so that it's easier for potential purchasers to get a feel for the game- as you noted, there's not currently any outside sources to seek reviews from (though one Steam reviewer did link a youtube playthrough, at least).