Two different types of yeast?

the beer i'm getting ready to brew is a "belgian" style but it's described as a nontraditional belgian. and the recipe calls for two different types of yeast and i've never seen that before. just wondering if that was normal or overkill and is there anything i should expect when using two yeasts? thanks

Some yeast strains will not attenuate a high gravity beer to the desired level.  A second strain can be used to finish.  In some cases, people have experimented blending strains (While Labs and Wyeast have several mixed strains) and liked the results.  It is helpful to know the reasoning behind it.  A lot of things sound reasonable but are just hokum. I encourage you to find a beer that is similar to the one you ware making and try it to see if you like it.  You might want to alter the recipe to you liking.