Turning 4.0 Backwards

[Seatbelt]

So are there any tips and tricks for converting 4.0 backwards to 3.5? For example:, I have this 4.0 monster, and I want it to behave in a 3.5 way. So I pick a race/class/feats etc that best represent what it was supposed to do in 4.0. But the monster has an ability to push targets away x times per day as an immediate action. Its some kind of fear-mind affecting ability. It targets will defense at +12. So obviously it calls for a will save.. whats the best way to calculate DC? Is it as simple as adding 10 (so will save DC 22???) and call it a day? For a CR8ish monster that seems extremely high.

This is only one example but I'm sure I'll encounter other problems as I go along. So advice of any sort would be wonderful

[tcrudisi]

This seems incredibly complicated to me. Have you ever played 4e? By understanding how the monsters progress, it will help you go backwards with it.

For instance, monsters gain +1 to hit every level. So an attack that is +12 vs. Will defense will become +13 vs. Will next level, +14 vs. Will the level after that, etc. So unless 3.x DC's increase by one per level (on average), then simply adding 10 isn't gonna cut it. (FWIW, I don't remember how quickly monsters in 3.5 progress. I've done everything I can to forget about 3.5.)

[Lyndworm]

In 3.5, most DCs work off of this formula: 10+1/2HD+ability mod. For a Fear-based ability I would suggest using Charisma as the key ability. So assuming the creature in question has 8HD and 16 Cha, the DC would be 17. Make sense?

[Tehnar]

If you have something in 4.0 that is hitting a defense and you want to convert it into a DC for a saving throw try using DC=10+0.5*attack bonus; in your case you would end up with a DC 16 ability.

Its probably not the most accurate (Lyndworm posted a better way), but its very quick and I think it falls in the ballpark.

As for the pushing away as a immediate action, just make it activate a free bull rush attempt without provoking a AoO; you can add some racial bonuses to that if you feel it is low.

[Prime32]

It helps to have a target CR in mind, so you can create an ability with the same chance of success against PCs of equivalent level.

[Sine]

If you have something in 4.0 that is hitting a defense and you want to convert it into a DC for a saving throw try using DC=10+0.5*attack bonus; in your case you would end up with a DC 16 ability.

Its probably not the most accurate (Lyndworm posted a better way), but its very quick and I think it falls in the ballpark.
Actually, balance-wise, you've got the right idea. (I'd tweak it to 10+.75*CR.) It's just not consistent with 3e's everything-is-based-on-HD trend, but that's okay.

[Tyndmyr]

3.5 and 4 are not terribly easily convertable.

Sure, you can mimic the feel of something, sorta, in the other system, but it's no more precise than statting out your favorite superhero in D20 stats.

[Erom]

The formulas derived when the forums discuss something like this tend to be pretty damn useful, though, so who cares if it's an easy conversion?

[Callista]

D&D 3.5 and 4th ed. are not the same game. They are, in fact, completely different systems; and conversion is about as difficult as it would be for any two completely different systems. Just because they are both called D&D does not make them remotely similar... They keep the base stats and some of the skill mechanics and that's about it. There's no simple formula and there never will be--not like with earlier editions to 3rd, which were much more similar and relatively easy to convert. You will be effectively creating a homebrew monster with the same fluff on his abilities.

I suggest you look at monsters of similar CRs to the CR you want the result to be, and simply create one with abilities in that range.

This wouldn't be a straight fear effect; it would probably be a spell-like ability based on fear (and using bonuses and immunities to Fear as normal).

As for save DCs, a good rule of thumb is to ask yourself what kind of DC a spellcaster PC of that level could be logically capable of producing.

[Seatbelt]

I know they're completely different games. But this is the internet. I figure somewhere some fan figured out a way to make it work. But thanks all. This is sufficient advice to do what I need. :)