There will be interesting special events called Retro Royale. Its cost 10 gem per entry. You play like it was back in the day using classing cards.
Furnace, ice spirit, ice golem are not exist in this retro royale challenge. You can use old meta deck such as hog rider + freeze spell, giant + poision, balloon + rage and ect. You can also use the most popular Jason deck. (Giant,Archer,Hog Rider, Arrow, Elixir Collector, Minions) . Unfortunately, the elixir cost 6 instead of 5.
The good thing at 5 win, you will get a magical chest and at 6th win you will get 3000 gold with just 10 gems.