[@ClocktowerEchos] One gun and one close combat weapon is hardly a "walking armoury". Yes, you are right that Nulls are not particularly intended to be active fighters. Given that they are relatively rare and valuable assets, however- insofar as human bodies can be considered "valuable" in the Imperium- it makes sense to arm, and to an appropriate extent armour, them on the off-chance that they do get into a fight, for instance if they're ordered to help their Inquisitional master in a firefight. And as far as fights go, it only makes sense to arm somebody with a strong weapon, which bolt pistols evidently are in this case. Once again, I admit that I may have underestimated the caliber and recoil of such, and have further stated that I'm willing to make it a las/autopistol instead (as well as the fact that it will reduce his firepower, because it is literally true that bolt pistols deal more damage per shot than their las and auto equivalents). It's also been described privately that marching around in carapace armour is not suited for Ollum's Inquisitor's style of action, so I'm more than willing to remove that from his wargear too.

As for the sword, is there any particular reason he shouldn't be trained in swordsmanship? Swords are reasonably common weapons in the Imperium, and undoubtedly deal more damage than knives, which matters more in this setting than in the real world even at the more basic levels, because knife stabs don't actually kill people immediately unless a few specific spots are targeted, and may not penetrate armour that a sword would deal with more readily. Also, since his fate outside of the Inquisition would likely have been the ASSASSIN Temples, to be trained as a Culexus ASSASSIN, and given that the Schola Progenium teaches its wards how to kill things anyway, it seems quite reasonable that he'd have started training with both knives and swords at the Schola, then continued his weapons training under whichever Inquisitor picked him up from the temple, say Inquisitor Karthis prior to his death. If it simplifies matters, I can just say his melee weapon is a "close combat weapon", make it maybe a foot, foot and a half long, and just leave it at that. You can conceal that sort of blade length reasonably well, if I'm not mistaken?