The Illuvian on the left side of the screen has one Battle Boon (the green slot with a white “>” symbol) and two Battle Conditions (the black slot with a white dot and a red slot with flames), shown in the pentagons next to the big “B” and “C”. If you compare to the Naltair on the right, the respective pentagons are all empty.
Even though there are three slots shown for Boons and Conditions each, a Creo can have more than three.
Each Condition and Boon has a certain Duration of turns before it will go away.
For any Condition or Boon, if the status effect is placed on a Creo a consecutive time before it went away the status effect will move up to the second level (if applicable) and the Duration will be increased. The Duration caps at 5 turns, and you can see how many turns are left in the duration by selecting and holding the status effect you want to look into.