The above post sounds interesting, however my news feed it actually says:
◆Event
The new EVENT GACHA has been listed! Check out the NEW SPECIAL CARDS you can receive, level up your old ones and get ready for the upcoming event!
Now in the event gacha screen if you check the card details it actually says the girls give an SED modifier so that bonus doesn't really apply to what's described in the above posts event features.
And of course off their Facebook page.

Originally Posted by Xanthius

"There's a new event gacha live on PeroPero! Check it out now and get those new girls for the upcoming Elite Guard event."
-From Nutaku's facebook page

So yeah that event type isn't quite here, although from what I've seen on Youtube there's certainly more event types, I wonder why they're reusing one so soon.

Also just a quick point about the current slayers, if you have all the slayer girls you can multiply your SED by 2.6 or 3.3 if they're all maxxed, they must seem pretty OP in Elite Guard if you don't have them.