Swarm is a very enjoyable PvE bullet heaven mode that Riot has introduced in League of Legends with patch 14.14. The objective is to unlock and go to different maps and regions to complete quests and fend off invading hordes.
Each map will have special features, that you will be able to use to your advantage as you make your way through mobs and bosses helping your favorite champions grow stronger.
You will eventually be able to unlock the Hard and Extreme difficulty game modes in Swarm as well. These will dial the combat challenge up by several notches, but you will get a lot of bonus EXP and resources if you can complete them.
All League of Legends Swarm Maps and how to unlock them
There are currently four maps that you will be able to unlock in League of Legends Swarm. Riot has given them each their own unique boss, mechanics, and unlock requirements.
You will be able to spawn the map boss by just surviving for 15 minutes. The bosses are incredibly challenging and as the game mode is designed to be a rogue-like, you will be dying a lot in the early stages.
Here is how you can unlock each map in Swarm:
1) Warehouse District

This is the first map of the game mode which will be available to you by default. It will have a healing fountain that you can use to heal yourself and your party members. However, after using it it will take some time to recharge.
2) The Outskirts

You will gain access to The Outskirts after you have completed the main questline in Warehouse District and defeated Primordian Rek’Sai who is the boss of the map.
The Outskirts’ map feature is an Obelisk that acts as an Ion Cannon. You will find Fuel Cells there that you can gather and use to fill up the Cannon’s charge. Once the charge it full, it will deploy a blast that does massive damage in a large AoE.
3) Subterranean Lab

The Subterranean lab unlocks after you have completed The Outskirts. The special feature of this area is the Freeze Bombs. You will be able to activate it by standing on a platform.
Once the bombs go off it will deal damage in a large AoE around it, while stunning enemies that are caught in it.
4) The Beachhead

The Beachhead unlocks after you beat Primordian Bel’Veth in the Subterranean Lab. The special map feature is a roaming Commander Fortune who uses a Bullet-time-like ultimate every now and then.
If you stick with her, she will help you trim out the invading mobs and make completing the objectives easier.
Additionally, the final boss of the map is Primordian Aatrox. He is the one and only two-phase boss encounter in League of Legends Swarm.
How to unlock Hard and Extreme difficulties in League of Legends Swarm

You can dial up the challenge by several notches after you unlock the Hard and Extreme difficulty modes in Swarm. The Hard mode for each of the maps will be unlocked as soon as you beat the final boss of the story mission.
So once you take out Primordian Aatrox in The Beachhead, you will gain access to Hard mode for each map. As it’s a higher difficulty level, you will get your hands on more EXP, gold, and upgrade materials.
To unlock the Extreme difficulty mode in League of Legends Swarm, you will need to complete each of the maps on hard. Extreme is not advised for casual players, and we recommend you try it only if you are serious about minmaxing your champions.