In Vendetta we will get a new Legend, Kennen. Chaos (purple) and Order (yellow) are its domains. This means we can combine Baited Hook with Nocturne. If I activate Baited Hook and in the 5 cards I look at, I get a Nocturne and a unit with Legion, would I be able to play Nocturne with his own ability and then the Legion unit through the Baited Hook and get its Legion effect?

Yes, this works. Nocturne gets played via his own ability during the Baited Hook look, then Baited Hook plays the Legion unit. Because Nocturne finalizes before the Legion unit (pending items finalize oldest-first), the Legion condition — "another card has been Finalized this turn" (Rule 812.1.c) — is satisfied, and the Legion unit enters with its Legion ability active.

The full sequence during Baited Hook's resolution:

1. Kill the friendly unit (creates any Deathknell triggers as pending).
2. Look at top 5 — you see Nocturne. His ability lets you banish him and play him for [A] (any rune). Nocturne goes on the chain as pending.
3. Baited Hook continues — Nocturne is no longer "among them," so you pick the Legion unit from the remaining cards and play it (ignoring cost). It goes on the chain as pending too.
4. Recycle the rest.
5. Baited Hook finishes resolving. Pending items finalize in order: any Deathknell triggers → Nocturne → Legion unit. Since Nocturne was already finalized, the Legion unit's condition is met.

One heads-up: make sure the Legion unit's Might is ≤ the killed unit's Might + 1 — Legion doesn't help with that requirement, so you'll need the stats to line up.