This is kinda late, but I tried the fix... there's nothing but two ladders... as soon as I stepped away from the first ladder, fell to floor because no floor up there to stand on...
Besides maybe jumping to the next ladder, I guess it would be necessary to jump to the altar also. Lots of trouble, it's much simpler and easier to hex edit the save to get to the top of the regular tower...
I'm sorry that my response is even more late, but since everyone who wants to play an urgoth in 1.5 will probably be directed to this thread I hope it's okay if I reply. Cause I'm sure there are a lot of players who would like to circumvent the urgoth bug and probably some of them will rather use my method than multiplayer (especially if there is no network with which to host a game for a second player, which definitely is the case for me! I can only play multiplayer alone). Yes, there are only the ladders because the tower is removed. What the player has to do is climb up the first ladder, stand on top of it, then do a leap of faith to the other ladder, pressing the "use" key in order to avoid falling down. If done right, the character will climb up the second ladder and hopefully stand on top of it (yesterday my Dwarf somehow took a step forward after climbing up and plummeted to his death). Then there is one more jump to do: from the top of the ladder to the top of the altar which is now floating in mid-air. Now the altar can be activated.
The way back is tricky: the player has to jump back to the ladder and climb down, but now it's (almost) impossible to jump over to the other ladder so the player will inevitably fall down. Hopefully (s)he has enough hit points and acrobatics skill to survive that fall
. If the player did not kill the mush men and shade, they may all be waiting at the spot where the player will land after the fall, so you better get ready for a fight.
And all of this means that now the term "ordained favor" has his real meaning: only a skilled player will get the favor!