Board Thread:Warhammer 40k General Discussion/@comment-94.3.72.36-20131224225315/@comment-8881468-20180404221136

the "brain damage" came from getting implanted with the butcher's nails, not more, not less, which is also the reason for angron to actually not use the means he had to his advantage but merely slaughter his army and actually failing at conquering the planet he landed on, something that other primarchs, who faced worse odds (see khan,lorgar,corax,curze) all did manage to achieve.