The boss only dimension is one of the Hardest you can get, unlike the overworld, everything's a Hostile Boss, with atleast 9000 Heath Bar's. You will need to be equipped highly to build this dimension you need, Here is the picture of how it look's, ( I made the picture myself ) Once you build it you will wait im sorry i forgot you can't build it, since the dimension is hard finding it is hard also, so once you find it it will be locked under iron bar's that are instead of iron, but some flashing version of it,
Pig Boss[]
Once you get in the dimension, you will spawn, if you see the nearest pig, you will see a Boss Health bar and fighting it is very hard, The Boss Pig's will love to call it's freinds over, it's boss freinds will have boss bar's too, but the first one will be 20x bigger than them he will have a king hat, once you kill it it won't drop anything but it will resort to Phase 2, you can tell when it get's to phase 2, when lightning strikes it dead then some Giant Zombie Pigman take's it's form, Phase 2 is different htn Phase 1, It will start running to you madly fast, then it will cause it to summon over 3000 regular Overworld sized, Pigman's, when Phase 2 start's getting weaker, it will drink a potion giving it 4 arm's and wings, The Zombie Pigman will start mutating into Phase 3 it's final phase, It will have have one Diamond Sword on one hand, The Second will have a small version of a tnt cannon in his hand, the 3rd hand will have a Pig Head, that spin's and fire's fireball's every 3 sec, and the 4th hand will have a bow. Once you kill it, a whole bunch of regular size pig's will drop out of the sky, and some of the grass, will lose some of it's plae color and turn a bit regular.
Creeper Boss[]
The Creeper boss is one of the hardest in the dimension, It will charge toward you, it still has Boss Health, It will run and explode on you until you kill it's 1st Phase, you will lose hearts as if you where exploded by a regualr one, but instead this one does 50x Tank Damage, you must have tnt armor to resist it's blow's, once you kill it it, will explode and float in the air, then it will start glitching into Phase 2, where it looks 20x bigger than earlier, it will some how get the abiltiy of Elemental Power's and start making it flood badly fast, in order to save yourself you must be equipped with Swimmer's there a armor than can be found in the dimension in a cave, Once you swim up to it will use physcic ability to kill you, it will throw you on the ground more than once as if it was ragdolling you, then it will do a a mind trick, u will lose control of you character, it will make you walk to the nearest Kill Me Pit where if u do step in it it will kill you automatically, to gain control so this wont happen, keep clicking then you will gain control, once agan, once you kill it it will die and regular Creeper's will spawn, soon the grass will turn a bit more, regular,
Iron Golem Boss.[]
W.I.P - Hey how about you add the mob's hard level to it