If you can run past the entrance stuff, the underworld has several 100% safe areas.
My personal favorite is to go like you are going to the Abyss (run past the bloodworms & blood elemental, of the latter is present). Take the teleporter across.
Now, walk back onto the remnants of the broken bridge the teleporter bypasses.
Use teleport (with scrolls if not a mage - 3rd level scrolls go off at 1st level difficulty, so even someone with 0 magery can do it), and teleport down to the single block between the two cascades.
There's room for up to 9 lobster traps down there, and 4 areas you can cast into, without teleporting again. If you fish out the 4 spots, you can teleport under the south end of the ruined bridge to find two more resource squares to fish (room for 3 or 4 traps), and you can teleport from the bridge footing and back to the single block as often as you want. The Blood elemental, etc. can "see" you, but not target you. The same probably holds true for others targeting you, when under the bridge, but the single square would probably be vulnerable to ranged PvP attacks from the bridge top in the same manner as you can teleport down, on SP & Mugen.
