Don't worry, it's been happening for a while. There's tons of 18+ ads and those click-bait ones but as long as you eventually get them closed you're good. Some of them will use pop ups to stop you from closing them so you have to make sure to close the pop up and then the tab itself.
It's a game of itself, really. I find it fun seeing if I can close the advertisement before the page even loads. But, yeah, these can't be controlled and FeralHeart is a free game so they're not going to make their forum free of ads with no serious funding. They don't do any harm unless you go with them, really.
I actually went along with one of those 18+ games and it told me that the game didn't even exist anymore. Pfft, it's funny, really.
But, yes, adblock-- numerous adblocks can't get rid of them. I've tried but no cigar. It's just a matter of dealing with them. Sorry about this but it's borderline impossible to get rid of them.