From his two high-level demon king slaves, Ajax got brief information about Daen.
Even though he was a peak high-level demon king, he was able to defeat three demon apostles before taking full control of the golden demon army for this invasion.
So, Ajax felt, that taking care of Daen was much more important compared to the other demon apostles.
'Even if I use the elemental spirit merger bloodline to merge three elemental spirits, Dean won't have any problem in taking care of himself. However, if the protector spirit beast can receive the help from the merged elemental spirit, then it might change the outcome of the battle.'
Ajax was not keeping his complete hopes on the merged elemental spirit; instead, he was just hoping the merged elemental spirit could help the protector spirit beast a little.
'Elemental spirit merger bloodline, activate.'
'Zen, Septon and Nite, Merge.'