Originally Posted by Obrysii
Thanks for the link.
Expansion (Augmented) would be a two-size increase item - and the big difference otherwise is Expansion works on non-humanoids, where Enlarge Person does not.
If allowed, it would (for some duration) make me Gargantuan ... dramatically upping my combat and mass-transit ability.
Having discussed with real-life friends, it seems my strategy should be using that lengthy tail of mine to trip opponents. In general, it appears that natural weapons do not provoke AoOs from trips (we can't find anything that says they do) and as a Large quadruped, I'd have a +8 bonus on them. If you ruled my tail does have extended reach, that'll just assist in that way.
The effect seems reasonable. I'll have to work out a suitable cost unless anyone has an example costing to hand.
To be clear, it would grant the size and stat changes listed under the expansion entry (+4 to str, etc.). Because you were bigger it would also increase your damage as per the Dragon Space/Reach, Attacks, and Damage
table in the Monster Manual. This also grants the crush and tail sweep special attacks, and increases the range (but not damage or save DC) of your breath weapon.
Tripping with a weapon, including a natural weapon, does not provoke. However, only a limited number of weapons can actually do this. I'm willing to add your tail (and only your tail) to that list. You don't get extra reach with your tail.
As a large creature you get +4 for being large and you add your str bonus. As a gargantuan creature you would get +12 for being gargantuan and add your (improved) str bonus. You only get the quadraped bonus for resisting being tripped.
The nice thing about tripping is that you ignore BAB entirely. It's just strength and size.
If you fail to trip your opponent, then as usual they get a free attempt to trip you. You can't drop your weapon to avoid being tripped because it's attached to your spine.
Note also that tripping does no damage. It can be very effective at stopping opponents getting into attack range though.
Also, fair warning, you're likely to get into situations where there simply isn't room for a gargantuan dragon.