Players can enter the Underworld by tapping the icon on the bottom right of the map. The first time a player enters, they need to enter their username, with minimum 3 letters and maximum 10 letters. Only latin letters and numbers can be used (space cannot be used). Once the username is chosen, it cannot be changed.
Each boss has a shield and the players must destroy it within a given time frame before they can finish the boss. After all the shield is destroyed, players can finish them. If they lose, they can repeat the fight until they won. Each raid-fight consists of one round, with every round lasting for 45 seconds. Players can buy several items like charges of darkness to aid them and deal additional damage. There are certain things that makes the raid-fights different from other fights:
- The level and stats of all equipment does not affect raids much. What affects more is the enchantments on these equipment.
- No perk works in raids.
- Underworld bosses are more aggressive than other bosses.
- They are also immune to the Stun enchantment.
The first tier of the Underworld. There are four bosses in the first floor.
Special Bosses Edit
They are the special bosses encountered in the first floor, available to be fought during the special event of the game (Halloween and Christmas). Fight with them carry random rules in each round.
Underworld : Tier 2 Edit
Underworld: Tier 3 Edit
This tier has one boss whose name and appearance is currently unknown.
??? - Requires Dan 8
There are various items available which can help player in beating the bosses. They can be obtained by defeating bosses, completing daily quests, or be bought from shop.
Charges of Darkness are items that can deal damage to the bosses. They work like thrown Magics, except for the Large Charges, which have a unique animation. When throwing a Charge, the character will become invulnerable to melee attacks.
- Minor Charges of Darkness
Deal a random damage between 75-84. Can be bought for 5 gems. It is the easiest charge to get. Player can get it as reward from beating any Eternals, daily quests, and at the end of season.
- Medium Charges of Darkness
Deal a random damage between 500-531. Can be bought for 25 gems or 175 gems for 10 medium charges. It is harder to get compared to the small charges. Player can get it as reward from difficult daily quests, at the end of season, and by defeating Fungus, Vortex, Fatum, Arkhos, and Hoaxen.
- Large Charges of Darkness
Deal a random damage between 1000-1021. Can be bought for 35 gems or 299 gems for 10 large charges. It is the hardest charge to get. Unlike the small and medium charge, the large charge cannot be dodged. Players can get it by reaching first place in raids with Arkhos and Hoaxen.
Elixirs are items that can give buff to the players, which last for one round. There are different types of Elixirs, with each type give different buff. Only one Elixir can be used for a round.
Players can withstand any Critical Hit without falling to the ground, similar to the Rock perk. Can be bought for 15 gems.
- Magic Source
Every hit taken will increase the players' magic recharge, similar to the Magic Recharge enchantment. Can be bought for 15 gems.
- Steel Hedgehog
Each time the players taking hit, they will reflect a percentage of damage to the enemy, similar to the Damage Return enchantment. Can be bought for 15 gems.
Player will receive rewards at the end of a season, which last for three days. The rewards depends on players' score and position at the League window. The rewards are a supply of small and medium charges, raid keys, and a small amount of gems. Players at the 1st-5th place also have a chance to get a random item from the Monk's Set. The Monk's item obtained this way will not come with the default simple enchantment.
- Main article: Dan (SF2)
Dan is a level-like system. All players start with Dan 1. By accumulating enough score, they will receive Dan upgrade at the end of a season, along with additional rewards. Higher Dan allow players to fight bosses with Dan requirement. Currently, the highest Dan is 7.
- Main article: Clan (SF2)
Player can join a clan or create their own clan in Underworld. Being in clan will give player the advantages to fight bosses together with their clan members, thus making reducing the bosses' shield easier. It also provides a better chance to gather players during match-up.
- Using certain weapon may allow the player to perform better in raids.
- Obtaining Ranged Weapon and Magic can increase the player's performance. Ranged weapon is unlocked after defeating Lynx, and Magic is unlocked after defeating Hermit.
- Enchantments can increase the player's performance. Players can enchant their equipment with Shadow Orbs that can be won from eclipse mode.
- Some daily quests can reward the player with Charges of Darkness upon completed. Charges can help players in dealing damage.
- Collecting the Monk's Set will unlock the Mythical enchantment Tempest Rage. Monk's Set and Tempest Rage can increase the player's performance greatly.
- Soon after the launch of the multiplayer mode the strength of the bosses' shields was decreased. However the damage they dealt was instead increased.
- All Eternals wield gem weapons.