Seems that you're limited on what Harry can do on the island. I'm pretty sure Harry has a bigger Arsenal than quicksand and intellectus. And I'm sure Alfred could physically whip dracul ass before ever came to blows with Harry..
Alfred is an ally not a power and harry’s Intellectus and his ability to manipulate the structure of the island are the only powers demonstrated by Harry to date as Warden. Maeve at one point neutralised Alfred with sufficient stacked Fae power, there is therefore at least one recorded instance that Harry could not rely upon Alfred as an ally on the Island.
We might in the future see other powers Harry has on the island, but it is impossible to speculate what they are as Jim hasn’t let on about them. The only potential new power is the tapping of the ley lines.
Against Blood On His Soul Harry would have a significant advantage with these two demonstrated powers, the Big Feet and their evil cousins seem to gain their power from the natural environment which on Demonreach are totally bent to Harry’s will, and his weapon. It won’t help to veil either, Harry’s Intellectus would discern the footprints of very big feet easily. Harry wins this one, rather easily, as Blood on His Soul wouldn’t be able to get within Head twisting distance of Harry. A couple of hailstones to the head at close range then fire.
Using these two powers Harry can take on any Fae on Demonreach, he knows where every discarded iron nail or rusty chain is located on the island. He can manipulate the ground to deliver them to where he needs them, in the case of iron nails into the soles of the feet of his adversary at considerable force when they are not expecting it. In an immortal Fae (Aurora, Mab, Erl King, Puck) Harry merely needs to immobilise them until his birthday, an non-immortal Fae is toast. Another Warden couldn’t kill an immortal Fae. Harry wins. Mothers appear to be immune to iron (Mother Winters iron teeth). The Mother wins.
Nicodemus Archelone, Harry uses the Intellectus to give him an advantage over Anduriel, when near some trees he uses a strong branch to grab him by the noose and a second strong branch to grab Nicky by the body and use the noose to pull Nicky’s head off. Easy win for Harry but dependent upon Harry’s special knowledge, another Warden would lose, Nicky could take to the air to avoid the Intellectus after an unsuccessful attack on him and attack that way.
Shagnasty still a loss for Harry on his current Demonreach powers, future power of tapping into the Ley line, maybe, but as an immortal he can reconstitute unless is is done on Halloween, so a rematch would be on the cards. Stalemate.
Mavra, easy win for Harry, his Intellectus trumps her veil, and I bet there is wild garlic on Demonreach, as well as every single branch and twig on the island a weapon against her.
Odin - still a win for Odin, he almost certainly knows all about Demonreach as his pupil built it. If anyone could anticipate and turn those powers against Harry it is Odin.
Hades - Harry is toast even if he taps into the ley line. Still far too powerful.
A couple of these wins and broken stalemates are because of Harry’s singular knowledge of his adversaries vulnerabilities, not just because of the Demonreach powers.
