Funny story, I needed a heart of praxis which I never yet obtained and an armentarium which I needed a 2,0 version of so I bought 2 engrams on my warlock first opening bam praxis, telling my friend in party he was like nice man, 2nd opening bam armentarium. Had 367 motes of light to blow and it only took 46, best damn luck I've had so far in this game!