It's a pretty nice idea. I mean, in my walkthrough of "Legend" I have not found a SINGLE Ancient Vampire for sale anywhere. With this training, you are ensured that certain units will always be in abundance - you just have to get their unupgradeded versions. Makes army building a lot easier. I already use it a lot to upgrade Swordsmen to Guardsmen. 
 
But yeah, if you don't need the upgrades, you are better off using the Shark's Tooth as it gives +5% XP and gold, as opposed to this one's +3%
		 
		
		
		
		
		
		
		
		
	
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