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The Hound - all units with 17-17-17 soul combination. (You can get the Silver Chalice with this achievement also)
The Enemy - all units with 51-0-0 soul combination.
The Rainbow - 51-0-0, 40-6-5, 26-25-0, 0-51-0, 0-0-51, 6-5-40 (in that order, you also get The Portal with this one)