They are repairable, but cannot have PoF used on them.
They used the 2-handed Paladin Sword graphic added way before AoS, IIRC, that was never used for a player weapon before.
they are 55% DI and undead/Demon slayer. Base Damage is 20-24.
They absolutely ROCK on the Dark Father. I was doing over 250 to the DFs with one, with the help of a friend's beetle. Plus, you can trigger whirlwind special move on it to clear out the mass of undead from the unholy bones, if they start interfering with your fight (pretty much 1-hit kills on everything with Lich HP or less - LLs take 2-3 hits if you are EoO on the DF).
Sure, it's a slow weapon - but it's slayer against EVERYTHING you'll face in a DF fight (and all but one of the rooms, but I switch to other slayers in the rooms to preserve the durability of the Redeemer) - and remember the whirlwind. And, the slow nature can save your life. Most of the time, if a DF blood oaths me, the slower swing speed gives me the opportunity to disarm or back off before I commit suicide-by-oath. I die 1/10 as much now using the Redeemer as I used to do even using a 15% SSI broadsword. Using a UBWS dagger or kryss was certain death, so I put those away when the DF got the ability to oath, after one trip to Doom.