Poetsword: I killed all 5 wizards
Raze_Larian: In the Black Ring dungeon, killing the 5 Black Ring bosses at the ends of the paths that lead south from the entrance should remove the spikes blocking the path north to the Demon of Lies. Are you sure you got all 5 of them?
If you use the teleporter stones to get past the spikes, does a cutscene trigger as you get to the final section of the path containing the fortress for the Demon of Lies? Until then your quest log will still list 'Stop the Summoning Ritual' and 'Kill the Black Ring' as unfinished; once the cutscene is triggered, the quest log gets updated.
If you can get to that building without the cutscene, then there was a problem with the quest status. If the cutscene is triggered, then the spikes not being removed was just a glitch, and you should be able to continue. If not, then it wouldn't do much good to continue, since a cutscene conversation would not be triggered later, and the Demon of Lies would not become hostile. In that case, try replacing the story files in a save before reaching the last section of the path with
these ones (1.2MB) from my save at that point (also included is the world.x3 file, with the spikes removed - this file keeps track of buildings, etc, the ground and items left directly on the ground in the Black Ring dungeon map).
If you don't want to bother trying the teleporters to bypass the spikes, you could just replace the files in a copy of your latest save to start with.
Is it supposed to be true that dexterity gives more damage for ranged weapons? Im not sure if strength adds to ranged weapon damage as it wouldn't make sense since I use a crossbow. In most games dexterity raises ranged weapons damage where strength does the opposite for melee.