Caxellac hadn't really been too keen to rely on extracting the Null Life Essence within this world because it was much too little to make too much of a difference in the grand scheme of the fight; where it was currently, that was.
While it was indeed in the billions – meaning Replicus couldn't even store it all in his body and had to cast the excess in Beyrmir's Storage Units – the damage Caxellac had taken, mainly from having his very cellular make-up altered to emerald, his armour, in particular, would require a significant amount of that reserve to fix. His brand of healing was only simple when he didn't have to reconfigure his entire anatomy after all, and that of the complex armour.
Said armour was the main reason Caxellac had been able to avoid certain death from Replicus' attacks – from the Fallen Reincarnator's Shadow to the Ju`wtte-enhanced punches – as well.