A new alternate Warlock portrait - Nemsy Necrofizzle - was announced by for Hearthstone yesterday, but it looks as though those who manage to unlock this character will find the cosmetic item locked to the region their account is registered in.
The news was recently confirmed on Blizzard's official customer service Twitter account:
While the blog doesn't specify, Id expect it to behave similar to other purchases/unlocks in Hearthstone which are not region wide ^KAL— BlizzardCS (@BlizzardCS) October 10, 2017
In order to unlock Nemsy, you'll need to attend an official Fireside Gathering during the promotional period. Assuming at least three players were in attendance at the community event, the registered host can then revisit the official Fireside Gathering site to unlock Nemsy for all attendees.
The problem comes from those with accounts registered in a country that's different from where they currently live. If your account is registered in North America but you've since moved to the UK, for example, then you will not be able to gain Nemsy by attending a UK Fireside Gathering.
This would appear to be a change of direction for Blizzard, given that previous cosmetic items - such as the alternate Priest hero Tyrande Whisperwind - are available across all regions once they've been unlocked.
Hopefully Blizzard will change its policy between now and the event going live, so that players who's circumstances have changed don't miss out on unlocking this unique item. We'll update this news story if that proves to be the case.