Ji_li_Tan
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So I am going to guess these mercenaries are a multi national outfit with bases mainly in Russia. Yangel seems like a Russian name according to Google and he has the bear motif, which is associated with Russia. They are supposed based in Northern Europe which includes the Nordics and Russia. Of course the name doesn't necessarily mean much, since the author had a Swedish mage named Tony.
For a 10,000 square metres, it only needs to be 100 x 100 metres, so not very large. This however is only the energy to destroy the buildings. Obviously the electromagnetic wave covers a larger area as he fries electrical devices in 5he 3ntire city.