i'm not seeing anything when Odin is lead and all other arena champions are void, also how can Varkos assist Pallus when Pallus uses its A1, says Argonites only and i saw it happen multiple times
Odin's aura just increases the speed stat of all other void champs in arena
Varkos's passive has a 15% chance to join in on any ally's attack. So when you see him join with Pallas, it's Varkos's passive activating, not Pallas' a1
Additional note, if you are running Mavara & Pallas together, Varkos will be joining a lot of attacks due to the constant Fervor Buff from Pallas combined with Mavara's Passive.