Ciders are a little trickier to get high gravity. Straight juice is somewhere around a specific gravity of 1.040-1.055 ish. If you ferment down to 1.000, that gives you an alcohol content of 4-5%. Now, throwing in "high gravity" yeast won't just give you a high gravity brew. You have to add fermentables somehow. That might be through concentrate, sugar, malt extract etc. There is also technique to this sort of thing. You can't just chuck yeast into a wort/must with a gravity of 1.200. You will need a MASSIVE starter to begin. It would also be a good idea to feed the fermenter incrementally to keep the yeast going.
There are some guys doing a SA Utopias clone here. Maybe check out that thread and see the techniques they are using. Brewing this high gravity is partly yeast, but a lot of technique too.