Roughly:

Levels:

1 feat: combat expertise+improved trip

2 teamwork feat: Tandem Trip

3 feat + bonus feat: Weapon Proficiency+weapon focus

4 +1 dex?

5th feat (Precise Strike?): ?feat

6th

7th feat+Bonus feat: Outflank + Weapon Focus

Alt: 1: Toughness + Evolution bonus point

Eidelon Ymir:

Levels:

2: Evolution?

3: Feat? Evolution?

4:

5: Con 14? Evolution?

6: Feat? Evolution?

7: Evolution?