User blog comment:DirgeOfCerberus111/Adeptus Custodes Vs. Grey Knights/@comment-2253300-20111028201241/@comment-1932673-20111028203650

Apart from the design from the runes AND the equipment used by the Custodes was created using forgotten tech, meaning it is superior to most GK equipment and the Custodes will power is as great as the GKs if not stronger. Also the Custodes are half way between a Primarch and an Astartes, now given the strength of a Primarch compared to astartes, even the Custodes could tear a GK to pieces. Also not ALL the GK are 'powerful' psykers for example Alaric and his squad in the GK omnibus seemed incapible of any offensive psychic power, plus the squads power is channeled through a Justicar, meaning that if the justicar is killed then the mental prowess of that squad is greatly reduced ant the GK powers are specifically anti Chaos and would be of limited use against the Custodes who are as opposite of Chaos as you can get considering the amount of time they spend in around the GT. Plus the GK do not have combat experience of 10000 years unless you are proposing that the majority of the Chapter have been fighting since the HH.