Al: Hold the bartering ram to test wether Dark Al is able to materialize a dark version of it or not.If Dark Al materializes it, do rock/paper/scissor with one hand, covering it by your weapon so Dark Al doesn't see your choice. After that, reveal your choice and see wether Dark Al got it right or not. Repeat 5 times (a decent ammount of times would take too long). If Dark Al guesses it right all the 5 times, we assume he can read Al's mind in order to mimic him. Otherwise, we may use the fact Dark Al needs to see what Al's doing to mimic him in our advantage somehow.We clearly need to find a difference capable of giving us an advantage, so this has to be tested.
Edit: We may also need to find out wether Dark Al is a darkness elemental/type or not. If, by any chance, we can harm him with an element that doesn't harm us, we can easily win this.
...of course that I'm unsure about wether we actually have a good light source with us or not.
2nd Edit: Hold on! Al already has the bulwark, while Dark Al still doesn't. Is there any chance we may be able to get an advantage from Dark Al requiring some time to invoke the bulwark before imitating Al? What do you all think?
This may be too risky to test, though, because if we do, we will have to either damage ourselves, or simply lose the opportunity to use the time advantage, as it will probably disappear (I doubt that he's going to be always one turn late because of that).
3rd Edit:
walk right, pretend to open door, walk through pretend door
I didn't notice the lack of door in our side... we should try this first. +1
I have a feeling that this will only work if Dark Al is unable to imitate us in case he doesn't see us, so we can perfectly skip my second test if we ever get to doing this.
Also, now that I think of it, we could try using Illborn Exchange. Dark Al simply can't be powerful enough to mimic an artifact like that.
What if we can capture Dark Al with the Illborn Exchange?
+1
4th Edit:
And now here come two silly ideas (possibly at same tier as the Al x DarkAl)
-Telling Al (I'm not telling Al myself to do this, hence the "Telling Al" rather than "Al:") to suck a bit of Dark Al's blood with his vampire powers. Would he lose blood and gain nothing? Would he lose blood and digest the same quantity of blood he lost? Would he lose blood and digest the same mass or energy measure of dark energy/mass/element/whatever as the blood he lost?
-Telling Al to become one with the Dark Al by trying to walk into the same space as him and attempting to use the Illborn Exchange at that place.
All of this written down, I think we have a lot of !!SCIENCE!! to do... but without the fire of everything burning down, of course.