HOW TO SPAWN THE BOSS AND STEAMROLL THE BOSS, EASY AND SAFE METHOD
Firstly this is an End Game achievement, one of the last you should get as you need a good understanding of the game in general and how to tackle bosses. Plus you need to have beaten the past and the high Dragun in order for certain NPCs to unlock to allow you to unlock certain items.
This method seems longer but it will save you time retrying runs as you can easily get a bad pick up or just not the pick up you want and you are in trouble. I am being super specific here as I had a lot of runs/wasted time due to a lack of information or direction.
The Advanced Dragun as a boss is no easy task to beat, if you beat Resourceful Rat, you could easily never recover the health you lost and without a strong arsenal you have no chance. This method makes the achievement really easy and ensures even average skilled players can get it. I tried the method of getting Gunther, then Weird Egg, RNG was a nightmare with many wasted runs and the Advanced Dragun has so much HP, it really is a battle of attrition or extremely high skill so let's take the route that will help most with the least stress.PRE-REQUISITES
You must have beaten the High Dragun on a Sorceress Run in order to UNLOCK GUNTHER
https://enterthegungeon.gamepedia.com/Sorceress You must have Unlocked Rainbow Runs and turn them ONRainbow mode or Rainbow Run is a game mode added in the A Farewell to Arms Update, activated by talking to the NPC Bowler, who must be rescued from a cell in the Gungeon after the High Dragun has been beaten at least once. https://enterthegungeon.gamepedia.com/Rainbow_Mode
Character: The Marine
Mode: Rainbow Run
RNG Warning: The only RNG in this game will be getting Clone in your first run through. Clone is really needed to make you OP enough to steam roll the second time around as when you die it respawns you on floor 1 with all your items and health.
1. Get Gunther
2. Get Clone
3. Get Gnawed Key
3. Perfect as many bosses and do as many floors as possible (Oubliette, Abbey and Rats Lair as you get 3 more chests (6 throughout with Clone)
4. Beat Resourceful rat boss and get him to drop at least 1 key on the Punch Out mini game (PRO TIP: hit him instantly by pressing A and he will drop a key every time this mini game starts). I never got past Phase 2 of this. Do Not USE THE RAT KEY, SAVE IT
5. Get to Bullet Hell (6th floor) as normal and get the Rainbow chest, then die and restart floor.
6. Get back to Resourceful Rats lair and repeat step 4 Make sure you save 1 Blank for AFTER the boss fight. With your 2 keys and 1 blank, open the secret serpents room (to the bottom left or Right of the item pedestals after the Resourceful Rat Boss) and feed him 4 junk so he follows you (open map, use left or right dpad to scroll items and press Y button to drop Junk
7. Get back to the Dragun and steam roll his ass
Tips for the run:
You can shoot from a door way into a room without aggroing/triggering the enemies inside. The gun you'll have has homing, is super powerful and most importantly has infinite ammo.
Clear Floor 1 and the boss flawlessly (no hit) this gives you the Master round which gives you another health up, we want to get 3-6 of these skill dependent throughout the run
Shoot all chests you encounter, you cannot pick them up but destroying them can give you Junk which you need to feed the Snake in the Rats Lair to follow you.
Download a Gungeon Item App on your phone so you pick the best Items. Do NOT pick too many Curse items as it makes your run harder, DO prioritize damage ups.
Detailed Method:Floor 1
- You need the Rainbow Chest to spawn Gunther https://enterthegungeon.gamepedia.com/Gunther
Keep restarting until you get Gunther, after you have him, clear the floor as normal and ideally perfect the boss. Use your blanks if you need. Save your money and do not enter floor 2 immediately. Exit via the Oubliette.Oubliette
Clear the floor as normal and pick up the True Abbey Shield after the boss but before exiting. If you get hit you cannot enter the True Abbey but it is no big deal.Floor 2
- Try and perfect the boss, buy the Gnawed Key (115 gold generally, should be affordable). Exit via True AbbeyTrue Abbey
- As NormalFloor 3
- Find and enter Rats Lairhttps://enterthegungeon.gamepedia.com/Resourceful_Rat%27s_La...Rats Lair
- Beat as normal, DO NOT USE KeyFloor 4
- As NormalFloor 5
- As NormalFloor 6
- Open chest and DIE, this is why you need Clone as you will respawn on floor 1 with all items and keys and now able to be OP for the Advanced DragunFloor 1 Again
- Save Money for Gnawed Key - Go to Oubliette again for extra chestOubliette Again
- As Normal, after you beat the boss pick up True Abbey Shield and then exitFloor 2 Again
- As NormalTrue Abbey
(Optional if you did not get hit) - As NormalFloor 3 Again
- Go to Rats Lair againRats Lair Again
- Beat again and get a key, open secret with your 2 rat keys Serpent room and use 4 junk to get him to follow you. Floor 4 Again
- As NormalFloor 5 Again
- As Normal BUT the Advanced Dragun will spawn after you beat phase 1 of Normal Dragun. By Now you should be INSANELY OP with Gunther and a range of Bullet/Damage upgradeshttps://enterthegungeon.gamepedia.com/High_Dragun#Advanced_D...
Cheevo UNLOCKED FAM!
Enjoy and I hope this helped :)