Druids aren't gonna like this!
Got a new one: Summon Monster IX. This spell is awesome!
Now i hear you ask: "how can this be? Have we underestimated the might of the Fiendish Dire Badger?" The answer, my friends, is yes and no. I wasn't thinking of Dire Bagers (fiendish or not) when i was typing this, but of d4+1 celestial elephants. (but you can use them as well for the following tactic.)
Picture this: You face a party of evil, high-level adventurers. Suddenly they hear a sound from above, look up and see 5 Celestial Elephants crashing down on them
I don't know exactly how heavy a celestial elephant is, but it's sure to weigh at least 1000 pounds. According to page 89 of the DM guide, thats 10d6 damage. Now summon them 110 ft above the taget's head, That's an additional 10d6 damage, for a grand total of 20d6 (The maximum possible for falling objects) damage!!!! The maximum range for MSIX is 125 ft (level 20:25ft + 5/level, i believe), so if you want to summon them 110 ft up, the maximum distance you can be from the target is the root of (125 squared - 110 squared), wich is the root of 3525 ft, wich is 59.37 ft. An elephant is Huge, so it's got at least a face of 10 ft by 10 ft, so you get a nice splash. Hehehehe...let's see a DM improvise his way out of this one...
P.S: The elephants can also fight, if they survive the crash.
P.P.S:This also makes the lower-level monster summoning spells better.
N.B: You can also summon Orcas, but i don't know if the are heavier or bigger.