Velen in The Witcher 3 isn't Geralt's favorite place since this land is full of swamps and monsters that hide in them, as well as in forests. It was ravaged by war and its people are experiencing some hard times. The only reason why Geralt goes to Velen in the first place is that he knows that Ciri showed up there.
But there are a lot more things to do in Velen than just looking for Geralt's adoptive daughter. Geralt encounters the local warlord, Bloody Baron, who asks him to find his daughter and his wife who went missing. And if Geralt is bored, he can always pick up one of the many contracts that Velen offers - some of the quests more difficult than others - and make some extra money.
The Beast Of Honorton
The Beast of Honorton ranks low in regards to difficulty since it's brief and only serves as a prelude to a much more significant quest Where the Cat and Wolf Play... Once Geralt arrives at Honorton, he only finds dead bodies and several necrophages whom he easily kills.
The Griffin From The Highlands
The Griffin from the Highlands is a contract that's easy to miss. It only becomes available once Geralt starts the secondary quest Master Armorers. Geralt then can go and kill a large archgriffin that resides near Crow's Perch. And since Geralt fought griffins before, killing this one is a piece of cake for him.
The Merry Widow
The Merry Widow has a recommended level 10. By the time this quest comes around, Geralt has already fought water hags whose behavior and style of attack is similar to grave hags. Therefore it's quite simple for him to bring the grave hag down and get paid for killing her. Geralt can find the notice for this contract in Lindenvale.
Woodland Beast
Woodland Beast is a quest that gives Geralt several options on how to proceed. He can either end up killing the beast - who actually turns out to be a group of rogue elves - or he can leave them in peace. If he decides to kill them, even though he's outnumbered, he can bring the elves down fairly quickly. Geralt can start the quest at the Border Post's notice board or by talking to the captain who issues it.
Mysterious Tracks
This contract will Geralt bring right into a territorial war between two monsters. Geralt can pick it up in Lindenvale. He'll eventually realize that the part of the forest where the cave is is a territory of two competing beasts - a fiend and a chort.
Geralt then has to lure the chort into the cave and fight it. The cave is fairly small which makes evading the beast difficult but Geralt can also harm it by using the relict oil which will make the fight easier. Plus, the beast is not as powerful as other monsters Geralt encounters in Velen.
Patrol Gone Missing
After a patrol of soldiers goes missing, Geralt gets the contract from their quartermaster. As Geralt investigates, he learns the missing patrol came across a wyvern and paid with their lives. Just like any flying beast, it can be difficult to strike the wyvern and some Witcher signs are less useful against it. However, since the contract's level is only 7, it's not as difficult as some other Velen quests.
Phantom Of The Trade Route
The above-mentioned contract isn't the only time Geralt has to take on a wyvern while he's in Velen. But the Phantom of the Trade Route is harder since this wyvern, unlike the previous one, is the royal wyvern. Geralt can pick this contract in three different ways - by talking to a refugee in Benek, finding the ransacked caravan, or by discovering the cave where the surviving refugees are hiding after they had spotted the wyvern. Geralt can use his previous experience from fighting flying beasts which makes this contract fairly straightforward.
Shrieker
Geralt can discover this contract on the notice board at Crow's Perch. The contract is challenging, albeit in an unusual way. It takes a while before Geralt can reach the shrieker since he has to drive the beast out of its cave first - by throwing a bomb at it. Interestingly enough, a lot of the players struggle more with figuring out how to get the shrieker out of the cave than with the actual fight. The shrieker turns out to be a cockatrice whose fighting style is similar to some of the beasts Geralt has already faced.
The Mystery Of The Byways Murders
Geralt finds a notice in Oreton that states a group of soldiers has disappeared. If he decides to investigate, he goes to Byways, a village currently full of ghouls.
After dealing with them, Geralt learns there's a vampire hiding underneath the village, and he takes on the beast. And even though it's only a lesser vampire, it shouldn't be underestimated - vampires are very fast and strong.
Swamp Thing
The swamps in Velen hide some dangerous monsters, such as an unusually clever foglet who lives in a cave. Geralt can either find the notice in Downwarren, or start the quest when he notices the strange fog. Either way, Geralt will end up fighting the foglet, and going against an enemy who can turn invisible is never easy.
Jenny O' The Woods
Even though this contract's level is only 10, it's one of the most challenging quests in Velen. Geralt can pick up the notice in Midcopse. As he investigates, he learns that the wraith known as Jenny o' the Woods was a local girl who ended up murdered by a man who wanted her for himself. The fight is challenging - it takes place in a small space, and Jenny occasionally calls other wraiths for help which means that Geralt has to take on multiple enemies.
Missing Brother
Missing Brother is one of the few contracts in Velen with a high difficulty level - 33. Geralt can pick up the contract at the notice board near the Inn at the Crossroads. He'll find the missing brother dead. He'll then have to fight several young spiders and later a huge spider that will not only use venom against Geralt but will also have the help of its children.