Hey guys I've been reading all Valiant since the relaunch and can explain some of the crossover characters. Both Gilad the Eternal Warrior and Ivar the Timewalker appeared in Archer and Armstrong because Gilad, Ivar and Armstrong are 3 immortal brothers with the last name Anni-Padda.
Loved Ivar and thought it reminded me of the first episode of the Chris Eccleston Doctor Who. Looking forward to more and can also recommend reading all the Harbinger trades from the beginning of New Valiant to present. It is a layered and powerful story.