How would you replicate Binding of Isaac in 3.5/PF?

[aleucard]

The setup looks interesting for a mini-campaign at the very least, and there's a lot of use that can be had from deploying the basic principles. Sure, several segments are likely to be contained within the campaign area so to speak, but having this serve as something to break up the monotony would be nice. Its modular construction (as in, EVERYTHING is randomized) also fits quite well with a pick-up-and-go quest if you don't want to do too much work that day. Making sure it's all balanced against the players may be a bit of a pain, but that's the way these things work. Not all of it has to come directly from Binding of Isaac either, maybe ether something completely new that just uses it as a base or something from elsewhere.

[Psyren]

3.5 Warlock + PF Young Template with tear-shaped eldritch blasts who has to find his essences and blast shapes in the dungeon?

[aleucard]

3.5 Warlock + PF Young Template with tear-shaped eldritch blasts who has to find his essences and blast shapes in the dungeon?

I was more thinking of something to let a standard party run around in this Pit of Madness. Trinkets and Items could be a form of new equippable with their own slot (which makes sense, as that's basically how it's done in the game), with the general stat-augments functioning as (maybe, depending on how self-contained this thing will be) in-dungeon-only grafts or something similar.

[eggynack]

I think the weird warlock method fits better, actually. You can emulate a pretty vast number of upgrades with eldritch blasts of various kinds, and you can even incorporate angel/devil rooms by introducing eldritch disciple and hellfire warlock as options, but only under certain conditions. The whole thing fits the general thrust of advancement pretty well. After that, you just have to incorporate the rechargable item/trinket system, as you mentioned, but that shouldn't be too difficult. Rechargables could be represented as something like eternal wands with their Isaac based recharge mechanics (perhaps with rate based on spell level), and trinkets are basically just standard upgrades that have their own slot. Doesn't work quite as well with a party, but I don't know if running an isolation based horror campaign with a full party is the best idea anyway.

[Troacctid]

I don't think D&D lends itself all that well to the Binding of Isaac style of gameplay. You could model something like it under the d20 system, I guess, but the feel of it would be difficult to capture.

For one thing, noncombat skills don't really come into play at all, rendering a large part of the system basically pointless. BoI also isn't designed as a team game. And a major part of its identity is its unique visual aesthetic, which is obviously hard to get across.

If I wanted to run a Binding of Isaac campaign, I'd start by using actual art from the game. Then I'd stick the players in a dungeon with no exit and have them go deeper and deeper into it with the enemies' CR gradually increasing until they eventually die. There would be no downtime and no resting, so magic would have to use a recharge variant. Then instead of items and xp, you'd collect upgrades, e.g. a wizard hat that grants you a level in Wizard, or a set of devil horns that gives you an Outsider racial hit die and the evil subtype.

[aleucard]

What I was envisioning is that this could be used as a substitute for the "Let's go to Hell" portion of the stereotypical campaign progression, or at least something useful for a short pick-me-up game a few sessions long. The larger the chunk of the campaign this is going to be, the larger and more numerous the "floors" get. Maybe this is the failed result of some Alienist/Demonologist or similar trying to make their own pocket dimension and the players are the poor sods tasked with making sure it don't spread. Maybe it's the successful result of the same and they either have something the players want or they're trying for their own "Take Over/Destroy the Multiverse" plan. It really doesn't matter what exactly brings them there, as long as they get to experience it. I'm more thinking of it being existential horror if anything, though again it'd likely have similar feel and purpose to a trip to Hell as far as campaigns go. Such is the nature of trying to do something horror-related in 3.5.

It'd be much easier to have the campaign there if more things show up than a refluffed Warlock. Nor do I enjoy the idea of locking the party into playing the same.