Aivenna is one of the top Overworld creatures in the game.
To start, she's got 70 health, which is one of the highest scanned energy in the game. Her wisdom and Courage are both extremely high, with her other stats being average. If you control a muge Aivenna's disciplines will all be boosted. Aivenna is the definition of a front line center creature. She only really has two avenues of attacks, Courage and Wisdom. With Outperform Wisedom and Outperform Courage, however, those 2 avenues are all one needs. While she doesn't have any elements. one could use that to their advantage. The best locations to use Aivenna in are Azaia Mindscrying Chamber and Numin Voidland, two locations that take away the elements of the opposing creatures, The Swartbron is another good location as she would most likely have the higher courage. Other locations that rely on Wisedom and Courage are all optimal for Aivenna. There are many creatures that work well with Aivenna. This includes Hune Paltanin to discourage opponents from using mugic, and Ikkatosh who would give Aivenna additional 20 health.
Directed Bravery is perhaps the best attack to use with Aivenna. A 2 build will do 35 damage due to her outperform abilities. All courage and wisedom attacks do an extra 5 damage which can quickly add up in any battle.
There are also many good battlegears to give her. Xerium armor would ensure she survived atleast 5 turns, if the opponent isn't using any mugic. Evergreen Tunic boosts her health by 20.
There are some problems. She's loyal, so she can't be used with non overworlders. She has zero Mugic counters. Her biggest vulnerability is other High Courage/Wisedom creatures like Tartarek, who she doesn't have enough of a lead to challange. She has no elements as well.
However her positives outweigh her negatives, and any overworld deck that uses Courage and Wisedom would be wise to add her.