As someone who definitely can't afford things like
Ancient Tomb and such,
Damping Sphere seems like a great idea. I don't know if resistance gives enough resistance to be worth it, but I think probably both inclusions would vary meta to meta anyway. Resistance would almost certainly make life difficult for
Edgar Markov type decks, but I don't see a ton of those anyway. Damping seems the more versatile of the two to my mind.
I tossed up
Possibility Storm but ultimately decided against it. We're not going to be casting a whole lot in general, so it's going to be a little weird trying to capitalize on it, which is where it's best. There's a chance it either entirely screws your opponents or backfires, and either way you can't control that, but because it applies to everyone you really want to be able to build around it enough to be pretty sure you can trade something like
Squee, Goblin Nabob that you really don't care about for something great like
Etali, Primal Storm or whatever. To my mind, this deck requires far too great a creature density to guarantee you can get more out of it than your opponents can. The other side of it that can be really beneficial is using the cast triggers for Storm-like mechanics. That's kind of wasted here. The final nail in the coffin for me is it's CMC, which is a bit high just for the potential of control with no real guarantee of advantage for you. Again though, it's a meta call - if you see heavy blue control you know counters probably don't resolve and you'll probably get good mileage.
Planar Chaos I can kind of see, although again it's precarious control because there's no guarantee it sticks around for any length of time, and once it's done it's gonna be likely gone for good - I don't know of any easy ways to get enchantments back from the yard in red. The casting cost is right though, so I'm more sold on this than Storm personally.
*edit now that I'm on a desktop:
I think the artifact lite/heavy discussion is a personal preference thing personally. I'm going more lite, but not entirely bereft, purely because the hand-filling capacity of things like
Sandstone Oracle and cantripping chump blockers like
Solemn Simulacrum and
Filigree Familiar is particularly handy, in that we don't necessarily need lots of mana, we need lots of cards in hand. Add to that the fact that literally all of our ways to cheat Purph's ability or abuse ETB's are artifacts:
Ancestral Statue,
Assault Suit,
Sundial of the Infinite,
Conjurer's Closet. Besides which,
Goblin Welder is worth running anyway for being able to protect these pieces to some degree, as well as being able to cycle your cantripping rocks like
Mind Stone,
Hedron Archive,
Dreamstone Hedron as well as being kinda cool with
Feldon of the Third Path and/or
Thornbite Staff for activations aplenty. I guess if you're going all-in on artifacts these pieces would be really clutch, but I'm going to be running these nonetheless anyway.
Thornbite Staff is a maybe, but I'm also running
Kiki-Jiki, Mirror Breaker so the potential instant equip and super token spam is undeniably great. I don't want to have Kiki able to go infinite so I am going to have to be pretty careful with other inclusions, but nonetheless
Thornbite Staff seems reasonable for those times you need a blocker and want a different way to get some extra value out of Purph's activated ability.