Treat tier 4 like all of the previous tiers. Fight and mine your way around towards the location of the final fight and keep going until you find the key you are looking for Elsword Gold.

Once somebody has the key, run back to the ice wall and rest until everyone is there and rested, the timer is capped at 5 minutes to kill the last boss and escape so if you have 7 minutes left, there’s plenty of time for people to rest.

Before you open the gate make sure the main tanker and all of the clerics are ready, they will be needed because as soon as the gate it opened the gold robber boss starts his attack.

Gold Robber Boss - Many people think that Gold Robber Boss is actually a lot easier than Gold Miner Marlone because it doesn't have an AoE attack which leaves fighters free to just attack it anywhere they want.

However the boss has the ability to stun with its normal attacks which then causes it to attack something else, more often than not an archer or a mage. So it is good to have a backup tank that can take over while your main tank is stunned.