Cassius - HC Untwinked Staff Charger

I'm still slowly forging ahead, and will update a bit later, but have a mercenary question. Since Cassius will be using Conviction, it seems like I should try to take advantage of the huge -resists by using a high elemental damage mercenary. On the other hand, the classic option of an Insight polearm is awfully tempting due to its huge damage, even if the Meditation aura will be redundant (and worse than Cassius due to no Prayer synergy).

I'm curious what folk think of the following runewords on mercenaries: Harmony, Obedience, Rift, Crescent Moon, Lawbringer. All of these seem like they'd benefit from low monster resists, but I'm also unsure if it'd make more sense to go with a Holy Freeze aura (+cold damage, slow) vs. plain ol' Might. I could also just go with a Spirit/Spirit Iron Wolf, but I've genuinely never heard of anyone using them.
 
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