Upgrading the evil shoal rage ability..

[Tuplis]

The shoal was one of my favorites too for a while but then it suddenly didn't get anything for like 6 levels. The shield on the other hand is excellent because it costs me about 7 rage and it'll absord even a hit of 10000 damage altho the strength of the shield is much lower. That's why I tend to send my dragons and griffins on very dangerous missions

The bottom line is, you have to adjust your strategy according to what you're being offered.