So the deepend would be a new area to the game. the enterence would be somewhere either near the tower or like in the mountain pass. the entry way seems to be somekind of big hole in the ground there's some sort of ruin next to it with a build able elevator or teleporter. basically once you build it (With rare materials: mythril, tons of crystals and maybe some sort of rune thing which is a rare loot drop somewhere.) It unlockes it allowing you to teleport into a deep cave I'm going to make two things that It could be

basically just a trial its more like a rogue like trial which once you use a pedestal you instantly lose all your loot (Its saved and given to you after) so how it would work is like the tower you have orbs in your belt except it isn't for checkpoints its for Skills: Skills are abilitys basically that you can use to your advantage in the dungeon like space. they consist of 2 main types each with 3 sub classes. the first is damage this consists of 1: melee which is close range stronger attacks like a slash and a shove. 2: ranged: it consists of magic bullets and beams that deal minor damage but are either fast and long ranged or slow and a bit more damaging. 3: outliers: anything that could be considered both or neither of the two like a slash that also does an air slice. the second type is passive/supporting: this consists of 1: healing: it basically heals you in anyway (if you were with another person some can heal them. 2: buff: it increased damage or defence or speed. 3:AOE: its basically an area of effect that can weaken enemy's or have passive healing of any friendly person around you or buffs nearby peoples strength or speed. that's the abilitys you can have 4 different ones and you start with 1 and can upgrade it over the time that your playing the game. so the goal is to clear as many "floors" as possible... it's like the mines except your doing one of 3 things on each floor 1: combat basically just fighting against enemy's. 2: survival: just survive untill the time runs out 3:peaceful/puzzle its either a rest area or a puzzle you have to solve requiring you to fine rune keys to unlock things or moving stuff to hold down a pressure plate. the rewarde increase every 10 floors up to 100 which is where the end is... you can continue (and maybe find another area) which maight not give you anything because the rewards cap at floor 100. at floor 100 you have to fight a boss which can be the ruined golem: (A terabada that looks more refined and man made. another boss is the rune dragon which is a blue and greyish with a hint of black dragon with a devastating Lazer blast. the last one is the follower a statue that looks like a person in a knight outfit. its the hardest to beat of the 3 due to its fast and devastating attacks.

that's basically it

the second idea is basically another mine with better loot with more crystal layers and different kinds even. also it would have a rare material which is used for endgame items. there would be a lot of terabadas and barely any wurms the terabadas are mechanical and the wurms are a lot less strong if they appear. the terabadas seem passive but if you get within arms reach they WILL attack you. they prioritize the wurms and can see that thay appear from all the way across the map. this area is a big dungeon and at floor 100 theres the same boss or bosses at the end. each dropping an item for something important later.

those are the two ideas. the areas are extremely dark with only slight lights around the place even some crystal light bulbs... its uses a more broken version of the tower stone and the celing loooks like it would break. its basically just a new area and i just wrote this because i thought of an idea. sorry for writing so much i just was writing for no reason feel free to ignore this post.