Like other shooters of its kind, there is a Redfall level cap that serves as the maximum prowess your character can reach. You can level up by taking down Vampire Gods, completing missions, ticking off Safehouse missions, collecting Redfall Underboss Skulls, clearing the Redfall Red Mist, and generally just being a vampire ass-kicker as you go about trying to survive in Redfall.
The Redfall level cap is Level 40, and this applies to each of the four playable characters you can inhabit in the game. It's worth noting that if you want to try another character, you will have to start the game over again - rather than being able to switch between them at will.
It's also worth pointing out I'm not entirely sure how you reach the level cap with any single character, as after completing the game and all its side content, my battle-weary Layla is only Level 22. In terms of repeatable content for pure grind, there's only really the Vampire Nests, which don't offer much in the way of variation.
With each new level that you reach in the game, you will unlock a skill point that you can use exploring each of the character's skill trees. They're pretty substantial, and they lean into the characters' unique powers, like Layla's vampire ex-boyfriend or Dev's Blacklight. They're quite mixed in terms of their focus though, with some offering buffs viable only through co-op play.
There are some that allow you to carry extra ammo, get more from health packs, and other more general perks, so they're well worth exploring fully when you start playing and levelling up.
Our Redfall review is here and Arkane's first multiplayer game isn't quite what we hoped for.