Figured it out. I was waiting for this week's update to see if there was a bug fix (there was not). Re-read the Wiki on this and something clicked finally. You'd think the purpose of this is to get a task for 100 kills, take some of these wildcards with you, and keep killing after the task is complete. That will not work.
For some reason they created these so that you have to have an active slayer task. So if you've completed a task and not gotten a new one, these will not trigger. You have to have an active task, and kill a slayer monster on the list that is not your active task for this to trigger.
I tested this in my POD. Had a gemstone dragon task. I also have an Abby Lord in that room. Took the wildcards with me while killing gemstone dragon, I killed an Abby Lord. Wildcard was consumed, slayer xp earned, etc. Of note - the drop was not anything special, so it's not like using these improves the quality of the drop. Without knowing for sure, it may be possible that they increase the odds on the quality of the drop.
23-May-2023 19:06:24