Goblin Slayer is based upon the light novel series and is a dark fantasy at 12 episodes long. You might go into the series expecting some cool fight scenes or an interesting story but what might catch you off guard after the first episode is how dark it can be. Right off the bat we're shown some disturbing scenes as it reveals the fates of several who had dared to hunt the goblins.
In this fantasy world, we follow an unnamed female protagonist whom we only know as Priestess. She is, as you'd expect, a priestess, specializing in healing and light magic. The series begin with her deciding to become an adventurer, starting from the lowest rank. She joins another group as they accept a goblin hunting quest. In line with most viewers' understanding, the group doesn't think much of goblins. They're the weakest of the weakest and are easy enemies for low ranked adventurers to gain some experience and money. Naturally, chaos ensues and we realize that while goblins aren't as smart as humans, they are not pure animals either. They can learn, devise traps and are cunning.
As the group falls into danger from the onslaught of the goblins they were hunting, help comes in the form of a fully armored knight known as the Goblin Slayer. We later learn that he only accepts quests that allow him to slay goblins, no matter how low the payout. All his gear is for the sole purpose of defeating goblins. He doesn't speak much and has an emotionless voice but as the series goes on and we start understand more of him, we know why.
After the encounter, Priestess decides to stay with the Goblin Slayer, forming their own party and assisting in the elimination of goblins. The anime has a good mix of humor stemming from the fact that the Goblin Slayer is so fixated on goblins. If what you're asking doesn't involving goblins in any way, then he's not interested. The fact that we never get to see his face and his steady voice makes it even better. While the anime is serious for the most part, there are some unexpected fan service scenes. However, some of those scenes just further warp the current situation and emphasize the horror and despair those characters would have been feeling.
Random goblin slayer can only keep you interested for so long. After a few of those, it starts hinting at a more sinister antagonist. The world is being plagued with the threat of a horde of demons. While it doesn't look like they relate to the outbreak of goblins in any way, you have your doubts. The goblins that the characters fight against seem to get smarter and smarter. They start off wearing rags and wielding clubs but eventually know how to use boats, wear armor and other things. It proves that you cannot underestimate them or you'll get killed.
Interspersed between the goblin slaying trips are slower paced day to day life sort of episodes. These episodes allow us to learn more about how the adventurer guild works, their responsibilities an the ranking system. It's an interesting way to fill in some time although at certain points, it feels as if it is following random unimportant characters instead of the main characters. The second half is mostly one long arc as the characters are summoned to a city and tasked with getting rid of a goblin infestation. It doesn't go as smoothly as what you're used to and the mystery is what keeps you intrigued. It never quite captures the same sense of hopelessness and despair as the first episode though but is still interesting enough to continue watching.
The final battle of the season provides evidence of the growth that the Goblin Slayer has experienced. He started off being alone, filled with his obsession and other adventures putting up with him. Now, he has a group of people whom he might call friends, and his social skills have improved. We get to see Goblin Slayer's knowledge about goblins shine as he predicts their every move, impressing everyone. The large scale battle is different to everything we've seen so far and the ending is all sorts of heartwarming goodness.
While the anime has stylized violent with a lot of heads being cleaved open, torsos sliced in half and blood splattering everything, it doesn't get overly excessive. It helps to portray that it is not all fun and games and the characters can find themselves in horrible situations. It's also interesting to see how the Goblin Slayer thinks up of inventive uses of conventional spells and items.
Overall, Goblin Slayer is a good surprise. It starts off setting the darker tone (which the brighter colorful animation may throw you off at first) but does a good job at alternating these episodes with more lighthearted ones. Goblin Slayer himself as a character is surprisingly likable as is the cast of characters that eventually become his party. Goblin Slayer is definitely a great anime to watch even though from an objective point of view, it doesn't quite do anything revolutionary or new.
--------------------------------------------------
For other anime reviews, have a look at this page.