Actually I think the Negative Spirit is one of the best ideas I've had (not saying its the greatest idea ever - I'm sure there are customs on the site with them that were made when only RotV was out). This alongside a negative aura makes it really give pause to opponent on whether to kill the unit first. Maybe they would change their strategy to use Unique Squads or Heroes without a special attack first and only kill [ON] after they are mostly dead as the Spirit does the most damage to Unique units with multiple normal attacks. But for the player this allows the unit to use the full aura most of the game, unlike Raelin or Taelord who are usually targeted pretty quickly.
The negative aura should be slightly better than the negative Spirit, and I think making people rereoll defense die is one of those that is sometimes powerful and sometimes not so I think is good to pair, plus I like it makes you think about it - I.E. if a hero rolls 2 shields out of 4 when you get 3 skulls - do you take the one wound or make them reroll hoping for more but possibly get screwed? The only thing I am not sure of if Aura of 4 is too good but I with this aura and spirit the unit should probably cost 120-140 or so (on par with or better than Raelin 2.0)
My
but I think pairing a negative aura with a negative spirit is totally a "Heroscape thing" and seems perfect counter to Finn/Thorgrim and this master set's version of Raelin.