For me, it was a ranged battle. My githyanki necromancer had a skeleton shooting squad of nine (four from Tav, three from Shadowheart). They took out the mind flayer quickly and then the intellect devourers as they approached. Gale, who had a flying ghoul, took out the Necromite involucres with Wyll who also brought his Cambion from the Infernal Rapier. I'd have to go back to the savegames for details, but my Tav blinked and misty stepped to Dame Aylin and ended Ketheric's immortality. I also had the Shadow from the Shadow Lantern, but I don't think it did much except for a few honorary hit points of damage. With all the ranged firepower, we took the apostle out before it could consume any necromites. At least, that's what the game achievement plaque says. My group was always surrounded by a host of thralls, so IP those battles were short bursts of violence, but IRL, it was a lot of clicking about and moving pieces about on the Lanceboard.
