Gaining 3rd domian?

[JoeGKushner]

Is there a feat or substitution level that lets you get access to another domain of your deity?

 

[Aus_Snow]

Bonus Domain, a feat from the Epic Level Handbook, also reprinted in Complete Divine, and perhaps elsewhere. Min. 21st level, etc.

There might be something else. . .

 

[Steve Jung]

It's not quite what you're asking for, but gaining the 4th level of the Divine Disciple prestige class from thePlayer's Guide to Faerûn would do it.

 

[Jack Simth]

The Cloistered Cleric gets the Knowledge domain, regardless of whether or not your deity grants it.

 

[Kwitchit]

Contemplative PrC (Complete Divine) can be entered after 10 levels of Cleric and provides a bonus domain chosen from your deity's list at 1st level and again at 6th. Apart from the high level, the requirements are very easy- and the class has full spellcasting.

 

[eamon]

The Complete Divine has a bunch of PrC's which grant extra domain(s). They're frequently written for a particular deity, but CD suggests that it's OK to reinterpret them with another, similar deity or alignment (talk to your DM yadda yadda).

Amongst those which cost caster levels to get an extra domain:

• Seeker of the Misty Ilse grants the interesting Travel domain, but requires survival ranks (but in turn has spot/listen as class skills)
• Radiant Servant of Pelor grants an extra domains and makes all healing empowered, and boosts turn undead power.
• The church inquisitor grants a host of interesting immunities, is accessible very early on (level 4), and grants the Inquisition domain (+4 on dispel checks)
• The Contemplative is an obvious choice with few drawbacks and useful immunities and an extra domain; however, it is rather high level.

I once made a character combining them all, which was funny, but not particularly useful and it requires very many skill points, so it's not exactly powerful (since you need to invest in a high int, and thus have essentially no dump stats).

 

[Nail]

Is there a feat or substitution level that lets you get access to another domain of your deity?

Contemplative PrC, CD

 

[Aleolus]

The Complete Divine has a bunch of PrC's which grant extra domain(s). They're frequently written for a particular deity, but CD suggests that it's OK to reinterpret them with another, similar deity or alignment (talk to your DM yadda yadda).

Amongst those which cost caster levels to get an extra domain:

• Seeker of the Misty Ilse grants the interesting Travel domain, but requires survival ranks (but in turn has spot/listen as class skills)
• Radiant Servant of Pelor grants an extra domains and makes all healing empowered, and boosts turn undead power.
• The church inquisitor grants a host of interesting immunities, is accessible very early on (level 4), and grants the Inquisition domain (+4 on dispel checks)
• The Contemplative is an obvious choice with few drawbacks and useful immunities and an extra domain; however, it is rather high level.

I once made a character combining them all, which was funny, but not particularly useful and it requires very many skill points, so it's not exactly powerful (since you need to invest in a high int, and thus have essentially no dump stats).

You forgot the Divine Oracle PrC, which gives the Oracle domain, which gives +2 caster level for all divination spells.
The Rainbow Servant also gives access to the Good, Air and Law domains as you level in it.
Seeker of the Misty Isle, in addition to the Travel domain you mentioned, also gives the Magic domain at 7th level.
Temple Raider of Olidammara gives access to the Luck domain at level 10

 

[Trouvere]

And then there's the Sovereign Speaker from Faiths of Eberron which in its 9 levels grants 9 domains from a wide list!

 

[Claudius Gaius]

Given that most domains consist of (1) access to a thematically-linked set of nine spells and (2) an ability comparable to a feat, all you want is a couple of feats - one which grants access to the spells under your usual rules for spell selection and one for whatever the special ability is. If you want a formal writeup, both are available in Eclipse (shareware version linked in the sig).