Which summons was this? Some runes can potentially create units that aren't the same faction (I have been avoiding/fixing these), thus it would cause disable Loyalty.
WAI. You are obtaining a rune from a potentially different faction. Looking over the Loyalty text, it is somewhat ambiguous as to what it'd mean.
The words DEPLOY and SUMMON have been fairly interchangeably used in Pox history. It's become more consistent that they mean different things recently, but it's still an issue in some cases (for example, all the "Deploy: X" abilities for relics).
It used to be that Summon and Deploy meant the same thing, at least in terms of descriptions. Summons didn't matter all that much back then because there weren't any real differences - they had presence, could contest, etc. For all intents and purposes, they were the same as a deploy and people weren't careful about which term they used. But that obviously isn't the case anymore. Deploy: X for relics have been largely summons for a long time and descriptions/names just never changed/fixed (I have fixed it for next expansion tho). Units is supposed to be CHAMPIONS + RELICS, but whether it is used consistently is fairly hit or miss.