I don't know if this is correct or not...

[Hario]

So lets say I'm a 17th level druid, I cast the spell Shambler, which creates 1d4+2 Shambling mounds. 6 max, 8 max if empowered through empower rod. I take the feat Concecrate spell and put it on say, Entangle. I then take energy substitution (electricity), since entangle now has an energy type which is (good) I change it to Electricity. For 17 minutes my shambling mounds gain 1d4 points of constitution per round. So after one casting of Entangle each shambling mound gains between 170 and 680 points of constitution and lose a point per hour. That is between 1870-3674 hit point increase and lose 11 points of constitution per hour. I know this isn't that bad, and any barbarian or most at that high of a level could still take them down. It just seems like much for a 2nd level spell, which by the time you are level 17 you can prepare over 6 of these, even worse if you are using spell point system which would be 92 times (though 2 hours more than a day). The spell Shambler keeps the shambling mounds around for 7 days or 7 months, if sent to guard a tower from invaders it very well could do it, and it doesn't stop one from casting this spell again and widen your entangle (electricity) for a total of 4 times a day by level 20 which can mean 24 shambling mounds to guard a city for 7 months while you are away adventuring and maybe hire lesser druids to prepare the entangles for your mounds.

[Clementx]

[Good] is not an energy descriptor, so Consecrate doesn't open up Energy Substitution. You have to use Locate City cheese to power up your shamblers. Which begs the question- why don't you just detonate all the other civilizations in the multiverse instead of trying to protect your own tower?

[Hario]

Because not all level 20 characters are evil bent on destruction? And I was pretty sure that [good] is an energy since concecrate spell says it changes the spell so half damage is direct damage from good. Again I could be wrong..

[Clementx]

You are. "From good" just means that you get to ignore the five real energy resistances (fire, cold, acid, electricity, sonic), which are defined in the PHB's Magic chapter.

[greenknight]

So lets say I'm a 17th level druid, I cast the spell Shambler, which creates 1d4+2 Shambling mounds. 6 max, 8 max if empowered through empower rod. I take the feat Concecrate spell and put it on say, Entangle. I then take energy substitution (electricity), since entangle now has an energy type which is (good) I change it to Electricity.

I don't think that would work with Entangle, but if you had a Wizard cast Wall of Fire (using Energy Substitution to change the type to electricity), and then make it Permanent. One casting would allow you to power up your shambling mounds for as long as you want.

[Jasdoif]

So lets say I'm a 17th level druid, I cast the spell Shambler, which creates 1d4+2 Shambling mounds. 6 max, 8 max if empowered through empower rod.

9 max if empowered. Empower increases the total variable effect by 50%, not just the die.

[UserClone]

The die is the only variable in that statement. The +2 is fixed, and therefore, not variable.

[TheSteelRat]

Things you could try that with
Thunderhead - lvl 1 spell (SC)
While you'd have to cast it for each of your guys, this would give you 17d4 extra constitutin, for an average of +42.5 (+168 HP avg)

Heartfire w/Energy Substitution - lvl 2 spell (SC)
This effects a 5-ft radius area, so you could get a couple of your buds in here. Duration is the same as Thunderhead, so you're just getting more shamblers in this one.

Fire Wings w/Energy Substitution - lvl 3 (SC)
Cool looking, yet practical. Duration of 1 min/lvl, so that's 170 rounds. Each round it's activate, can make up to 2 attacks as allowed by your BAB. So, you can cast it on yourself, and attack a shambler for a total of 170d4, or +425 average constitution (+1696 HP), which would run out after the 7-day Shambler spell ends. Or, you can split that total up among several. That's with one casting & several minutes(17) of smacking each other around. If you cast it more, yup. Also, it'll give flight. With electric wings. Bonus points for cool appearance factor.

Fires of Purity w/Energy Substitution - lvl 6 (SC)
Basically, every time your shambler is attacked or attacks, the attacker or the target gets hit with a little bit of lightning. Lasts 17 rounds. You can set this up a number of ways. If you can have your other shamblers attack this shambler, but doing non-lethal damage. Something could be worked out. Depends on your DM, but I'd allow "pulled punches" (attacks with 1 point of non-lethal damage) or something similar.

I'm sure there are other ones. Why not Flaming Sphere? Produce Flame? Better yet, Wall of Fire (Concentration Duration)?

Most of these options either take longer or effect a lower number of creatures, but they're the main ones I think you're looking for.


***** Edit ******
What about summoned creatures? SNA4 gives you access to Arrowhawk Juveniles, which can attack up to 17 times per casting. Using SNA5 or 6 produces more summoned creatures as well. Don't upgrade beyond Juveniles because you don't increase the # of attacks.

[KillianHawkeye]

The die is the only variable in that statement. The +2 is fixed, and therefore, not variable.

No, the variable portion is 1d4+2 all together, creating a range of possible random values from 3 to 6. With empower, the range becomes 4 to 9. It is explicitly stated to work this way. (The example in the PHB is for an empowered magic missle.)

[Chronos]

The die is the only variable in that statement. The +2 is fixed, and therefore, not variable.

The variable is the number of shambling mounds you get, which varies from 3 to 6. Empowered could (but is unlikely) to get you as many as 9.