This weekend it will be available in both the Event shop, and in the Soulforge.
Please note that some of the Social Collectibles that players can earn from this event were released with another event in the past. This means that some players may already own them.
@Kafka There seems to be a mistake in the in game descriptions. See the ss below. In events it says use troops from Khetar but in the RB battle page, kingdomg retriction is Swords Edge
This (Raid boss news page has weekly event kingdom named) has been happening on regular basis since time immemorial (perhaps ever since Raids became weekend thing, though not certain about it). People have mentioned it a few times, but no substantial result has come out of it.