The gate of fire is located in the dry lands of Topolo Durga which is situated beside Tetra Hill. The monsters within the pool of fire has high resistance from fire damage thus they have less resistance from ice damage so it is advisable that squads must bring Elementalists with them or any other characters that may decrease elemental damage from the pool. There are necessary strategy on how to manage the mobs and it depends on the strategist of a faction. Proper equipment is also required to engage in this raid instance and make sure you reach at least 57 DR (defense rate) and above to absorb punishment.
Now the faction must have at least more than a squad to summon Lava Leaf by activating pillars. And then do your best to slay the summoned boss. A good strategy is the key to finish this quest and you might get rewarded by an array of Fire Series suitable for the next instance mission - the Gate of Lightning.