H3110 guys!

After trying Hell & Back and reaching Shore of Hell, I have some tips for fighting a boss.

Before fighting a boss, summon a portal to the Lobby. This gives you a emergency second escape route other than the stairs, to earn time for regeneration without bumping into another enemy and keep yourself safe.
Always prepare enough medical supplies. This is very basic stuff, in case you takes too much damage. Meat Cans and Medkits are suggested.
Don’t fight alone. Having companions will further increase total damage output per turn, while someone will take damage for you.
Have your companions armed. Your companions will also pick up weapons automatically, and immediately arm.