Killer Troll uses Killer Wave and Cave Troll to wipe the board and and allow your Cave Trolls to survive. This strategy also focuses on keeping the trolls active, even through effects like transmute to butterfly and freezing trap by using orb of fluidity. Other key synergies to look for are Gifts From Above and Cave Troll, or Magic Tuna and Orb of Fluidity. Remember, playing anything that costs 4 or more forces your Cave Trolls to the bench where they are healed fully.
You may assume that this deck would only be blue and green. However, it's a 3 color combination, and adds black for Grave Uprisal, Vampiric Bite, Frighten to Death, and Engorger. Grave Uprisal will allow you to return your deceased Cave Trolls to battle and often allows you to make use of Develop at the same time, so your trolls return as 5/5 allies.
Killer Troll is filled with removal cards such as Freeze Trap, Vampiric Bite, Killer Wave, Frighten to Death, and Fresh Force. Grave Uprisal will also allow access to these cards again if needed. Here's an example deck list: http://orbsccg.com/decks/hjvshz
Overall, it's a fun control deck that plays out a long controlling game, killing with small allies by clearing the way, or using Develop to force its way through. A key factor for this deck is drawing cards so that you have options and a kill condition, most likely in the form of Cave Troll.