Despoiler or Chiron?

Chiron and Xekaar might get some game once Disciples of Agony drops. But that will require you to buy a bunch of Minions models....

Mordikaar is waiting for a theme list he wants. Void spirits getting shoe horned into Exalted Legions wasn't good for him.

I guess for now go with what you want to play more.

Both of them are fine, but they have very different roles. I think Despoiler have more action outside its host caster, as free upkeep, Dark Shroud and Arcane Suppression are all excellent support abilities. Despoiler works really well with Makeda1, Morghoul1, Zaadesh2 and Zaal2 as he can keep that one upkeep on and add some serious armor cracking value to your list. Chiron is much more straight forward playstyle with not too many tricks. In my opinion Chiron is more about offering infantry hate in form of powerful spray and keeping other basilisks in bay. In a way, Despoiler helps your caster do more while Chiron helps your army.

If you only plan on playing them with their bonded casters, then in my opinion Chiron would help more. Despoiler helps Mordikaar with infantry by making more void spirits, but is kinda predictable: it tries to get close to warrior models for void spirits. Chiron has some good synergies with Xekaar that really buff him. His spray combined with mortality can clear almost any infantry. Xekaars feat + spray can make beast heavy lists life hard especially if you also add agonizers maddening aura there. Overall Chiron is tough piece to remove under Xekaars feat (15/23 defensive stats with feat and agonizer). Chiron can help Kreas crack armor and manage drakes fury while they clear infantry...so yeah, I like Chiron and Xekaar combo. It's fun to play and fairly effective toolkit too.

Biggest ARM swing that you can make with Skorne faction is Rasheth with his feat and Blood mark while attacking Zaadesh1s tag teamed and enraged beast that is close to Despoiler. That is almost impossible to pull off, but offers hefty 10 bonus in damage =D. With that even a cyclop would deal around 40 damage to a ARM20 gargantuan. Highest damage under all those buffs would come from desert hydra (around 131,25) as it can get biggest number of attacks, but then again, would you really put desert hydra on Zaal1s battlegroup? Hehe. Aradus soldier would deal best damage out of our nongargantuans: 96,25 which is quite insane amount as well. Quite amusing calculations, really =D

Still one should not lock themselves to think that themes are only way to play, as playing out of theme might give you stronger synergies. 7/7 Makeda2 double ferox lists in WTC played Despoiler in it, just because it offers free upkeep and armor crack utility for Ferox and rest of the list. Other than that, there is only one non-bonded beasts on that tournament; Chiron for Hexeris2. It's not uncommon to see Despoiler in Zaadesh2 lists (for free cloud upkeep) or Tiberion with Naaresh (under feat its unmovable and unkillable) even though both would go fine in the beast theme. Themes are strong, but it's good to think outside the box sometimes and see if something outside the theme would be actually worth more than some free points.