First I'd like to point you to all the sources I know of about tricks and handling:
-PHB p.74-75
-Complete Adventurer p.100-101
-Arms & Equipment Guide p.75
-Races of the Wild p.146
-
Wild Life article
-Monster Manual II p.219 WarBeast Template (See the end of this post)
-
Wild Cohort feat to grant animal companions to all classes.
-Also, the useful
Handle Animals Guidebook
-I'd like to point you to Complete Adventurer p.101 with the feat: Extra Tricks that an animal or Magical Beast with an INT of 1 or 2 that already knows at least 1 trick can take, which grants the benefit of learning 3 more tricks than normal. This is a feat your animal takes, not the PC, based upon the animal's HD granting feats. This may end up replacing a standard feat the animal comes with, or if you have the ability to progress an animal's HD, you simply have the animal take it at the appropriate point in progression.
Finally:
-A shameless plug for why I know all this stuff,
How To Raise A Rust Monster Mount.
-A request for more contributions to the discussion of
training Dinosaurs and such.
I have several questions regarding tricks and animals.
#1. Can a usual Warhorse attack unnatural creatures?
PHB P.74 "Handle Animal - Teach an Animal a Trick" says that an animal with an can learn maximum of six tricks.
And "Attack" paragraph says Teaching an animal to attack all creatures including unnatural creatures counts as two tricks.
Then, P.75 "Combat Riding" paragraph says an animal trained to to bear a rider into combat knows 6 tricks including "Attack", and Warhorses and Riding Dogs are already trained to bear riders into combat.
Does that mean such a combat mounts knows exactly that 6 tricks, and thus not be trained to Attack unnatural creatures?
PHB p. 75 "Training Animals For A Purpose" provides packages of tricks. The advantage of training these packages is supposed to be less skill checks. To teach an individual trick, is 1 week. To teach the package "Combat Riding" is 6 weeks, but only a single skill check instead of 6 separate ones.
All the possible general purpose packages include:
PHB:
-Combat Riding
-Fighting
-Guarding
-Heavy Labor
-Hunting
-Performance
-Riding
C. Adv:
-Advanced Fighting
-Defensive Guarding
-Thievery
Races of the Wild:
-Helpmate
-Herding
-Rescue
Wild Life:
-Adventuring Pack Animal
Therefore to answer your question:
Can a usual Warhorse attack unnatural creatures?
The answer for the standard, vanilla, Combat Riding package trained "usual Warhorse" is it is NOT trained to attack unusual creatures.
However there is NOTHING saying that a Warhorse or any animal has to have been trained by only that one package (Combat Riding), or a package instead of separate tricks. You might assume the standard Warhorse is likely taught
those 6 tricks by the NPC handler you bought it from,
if that's how the DM played the NPC who the warhorse came from. If you're the one doing the training, you could select whichever tricks you want. You can also negotiate with your DM to have spoken with an NPC to buy a non-standard trained Warhorse.
If you end up with a Warhorse trained to attack unnatural creatures, and if the Warhorse can only have a maximum of 6 tricks, assume the Attacking unnatural creatures has taken up two trick slots, and lose one of the other standard ones from the list of (come, defend, down, guard, and heel).
Keep in Mind the Extra Tricks feat option.
#2. Making an animal companion into an effective combat mount.
Does an animal companion need to know 6 tricks (7, if you want to let it attack unnatural creatures) to serve as an effective war mount?
It seems to be rather ... hard, especially when a druid either release or lost an animal companion and then gain a new one. A new animal companion only knows bonus tricks as per table in PHB P.36.
Only a PC with effective druid level of 18+ can immediately gain an animal who knows 7 tricks. It seems that a less capable druid must train his new animal companion for weeks to make it an effective combat mount.
Note that there is no "Ride" trick. There is a riding package which includes "Come, Heel and Stay", however whether or not an animal can be ridden is usually based upon the creature description and the PC's Ride skill. The Warbeast Template (see below) grants in the text the ability for any creature to be ridden that can and has been trained into the template. So one can determine with the information in this post, if a creature can serve as a "Mount". The words "Effective" and "War" in your question...:
Does an animal companion need to know 6 tricks (7, if you want to let it attack unnatural creatures) to serve as an effective war mount?
...depend on what you do with the rest of the information in this post from these sources.
To be an effective war mount depends upon what the player expects from a war mount.
Let me list all the possible tricks from the available sources (some repeat):
PHB:
-Attack
-Come
-Defend
-Down
-Fetch
-Guard
-Heel
-Perform
-Seek
-Stay
-Track
-Work
C. Adv:
-Assist Attack
-Assist Defend
-Assist Track
-Hold
-Home
-Hunt
-Stalk
-Steal
-Subdue
-Warn
Arms & Equip:
-Don't Attack
-[Special Ability] (*worthy of special attention*)
-Alert
-Disable
-Disarm
-Subdue
-Trip
Races of the Wild:
-Ambush
-Bull Rush
-Disarm
-Mark
-Overrun
Wild Life:
-Ambush
-Bull Rush
-Flush Out
-Overrun
-Pin
-Stalk
If your Animal Companion can know up to 6 tricks, you have the appropriate level of Animal Handling skill, and you invest 6 weeks worth of time, YOU decide which of these options to teach. Have Fun.
If you're a Druid that has picked up a new Animal Companion, negotiate with your DM if the wild animal you picked up can have a different set of known tricks than standard. Many of the additional tricks could make just as much sense in the natural world for an animal to have then the standard set.
Again, Keep in Mind the Extra Tricks feat option.
I'd like to point out in the Arms & Equipment Guide, there is a list for Guard Creatures and Mounts. It's a very inspiring read and gives many creative options. The list of possible Mounts includes:
-Blink Dog
-Megaraptor
-Riding Lizard
-Owlbear
-Triceratops
-Worg
-Axebeak
-Hippocampus
-Couatl
-Dragon
-Gelatinous Cube
-Hieracosphinx
-Hydra
-Nightmare
-Purple Worm
-
Rust Monster
-Skeletal Horse
-Tendriculos
-Wyvern
-Equine Golem
-Zaratan
-Soarwhale
-Giant Ant
-Giant Praying Mantis
-Giant Wasp
-Monstrous Scorpion
-Monstrous Spider
-Giant Dragonfly
-Giant Firefly
-Girallon
-Grey Render
-Ogre
While many other books, such as Monster Manuals, offer additional suggestions for possible Mounts, I'd like to take a moment to highlight two of my favorite: the BattleTitan (dinosaur) from Monster Manual III p.38 (Cast an
Awaken spell on that thing...) and the Ashworm from Sandstorm p.140.
#3. Are there any feats, class features, magic items to help such clumsiness?
For some characters, taking Natural Bond feat (Complete Adventurer) and/or becoming a Beast Master (also in the same book) help raising his effective Druid level. But immediately gaining an animal companion with 6-7 tricks seems to be still hard.
Are there any other good method to solve this problem? Say, are there some magic items which immediately let an animal learn additional tricks?
-Extra Tricks feat, as mentioned.
-Monster Manual II has the incredible Warbeast Template. It's a trainable template that can be applied to any medium sized or larger animal, beast or vermin (but it later says that vermin are untrainable, so ignore that).
This template, requiring 6 months of training with a domesticated creature (longer and different DC's for wild creatures), grants +1 HD, +10 Land speed, grants a +2 to Ride checks to rider, ability to wear all types of armor, +3 STR, +3 CON, +2 WIS, +1 to Listen and Spot checks.
-Wild Cohort feat, mentioned at the top of this post.
-
Wild Life article has 4 new feats to aid a PC in working with an animal. It also lists out all the body slots that an animal may possess to equip magic items. Note that list, plus the armor granted by the Warbeast template, can lead to a very, very well equipped animal.
If you want to immediately acquire an animal or beast that knows a different set of tricks, talk with your DM. If these additional sources are available to you beyond the PHB, consider a Druid's Animal Companion's Bonus Tricks from other lists.
In conclusion, if a PC decided to make intelligent use of the options available here (Please take the time to read over my
How To Raise A Rust Monster Mount, it's long but inspiring, IMHO), you can likely even replace certain party members roles such as stealth, scout, thief and damage dealer with a well trained pet, at least at lower levels.