So I need something like a chaotic advancement table for goblins and some light rules with it to make it stick. I only have to come up with 19 (because, reading this over at Monster and Manuals, it's all about the math) fun ways to make this work...
Goblin escalation (1d8+1d12):
2 Delicate deformation: Maybe it was the waste? Anyway, now they mutate. Roll again on this table and whatever comes up is somehow related to the mutation.
3 Spontaneous animal control: You want a pig-stampede in your town? Didn't think so. But somehow the goblins not only managed to cut the animals loose for mayhem, they also seem to have a strange kind of control over them (animals worth 10 hd). Every time this comes up, it escalates even more (+5 hd every time).
4 Uncanny alchemy: They don't know what they do, but it explodes and they know how to handle that. Whatever strange ingredience they use, area of effect is 5 feet, damage is 1d4 and a save versus poison because of the wicked smoke this produces (failing means -1 to attacks for 1d6 rounds). For escalation either add 5 feet, upgrade to 1d6 (then 1d8, etc.) damage or -2 to attacks for 1d6+1 rounds. Repeat.
5 Gibbering goblins: Those guys talk gibberish and have a lot of fun doing it. You think, the words make sense or are at least in a language you know, but if you start listening, it gets irritating fast. Save vs. spell or be irritated for 1d4 rounds (-1 to all actions). If this comes up again, it's either irritating for 1d6 (1d8, 1d10, etc.) rounds or it's -2 -3, -4, etc.) to all actions. Mix according to taste.
6 Food enhancement: They found some food storage and are now with a full stomach! 2 more hit points per goblin every time this is rolled.
7 Unusual protection: Pots, pans, barrels, whatever they find, they use for protection. Every time this escalates, add +1 to the AC.
8 Leg fixation: This is like playing rugby. They run between the legs or duck behind you as soon as you step back. If fighting more than one goblin, DEX-check every round or you trip over one of them. If this came up more than once, it's -1 (-2, etc.) for the DEX-checks.
9 Joyful clubbing: They have fun hiting things and it shows. They get +1 to melee attacks. With a critical hit they hit a sensible area (grotch, eye, etc.). Roll this again and it's either +2 (+3, etc.)to hit or a sensible area with a attack roll of 19-20 (18-20. etc.).
10 Random hiding: Are they playing hide and seek now? For every goblin you're able to see, there is one hidden somewhere behind your back for a surprise attack. You can't shake the feeling that the one showing himself does so on purpose. If this comes up again, there are two hidden behind you.
11 Verbal humiliation: Are they making fun of you? They sure are laughing! Morale goes up +1 every time this comes up.
12 Speedy gobos: Sugar rush or coffee, they seem agitated. Whatever ini-system is used, they get a bit faster every time.
13 Painfull aim: Whatever they throw at you, be it book, vegetables or stones, it hurts. They get +1 to ranged attacks up to 10 feet away. With a critical hit they hit a sensible area (grotch, eye, etc.). Roll this again and it's either +2 to hit, up to 15 feet away or a sensible area with a attack roll of 19-20.
14 Sneaky buggers: Ah, they've just been here! But where are they now? You hear some noise or find a trail, but the goblins are gone already and it takes one round to catch up. Roll this again and it takes two (three, etc.) rounds to find them.
15 Manic manure: What? They are growing?! Yeah, one in six goblins is bigger than the others. As big as a (small) dwarf and with a lot of muscles. +1 to melee attack damage. Roll this again and it's one in five goblins (then one in 4, etc.) or +2 (+3, etc.) to damage.
16 Unfortunate ducking: Something seems always between you and the goblin you wanna hit. They always get a cover related AC +2. If a melee attack indicates a miss by one or two, a save vs paralysation is needed or the weapon is stuck for 1d4 rounds (STR-check possible every round). Roll this again and it's either AC +4 (+6, etc.) or stuck for 1d6 (1d8, etc.) rounds.
17 Coordinated backstabbing: One goes for the attention another, one for the liver. If fighting more than one goblin their dirty fighting tricks give one of them double damage. Roll this again and two of three do double damage and so on. If two of three goblins may make double damage, three goblins will attack one target, if four are needed, four will attack, etc..
18 Trippy traps: Buckets on door frames, pepper explosions, needles on unusal places, they booby trapped everything! Whenever characters search an area and goblins are around, there is a trap. Save vs. magic wands or (1d6): 1. 1d4 damage 2. blind for 1d4 rounds 3. nausea for 1d4 rounds (-1 to all checks) 4. cough attack for 1d4 rounds (-1 to all checks) 5. slippery ground and shards (no running, DEX-check or tripping into something nasty for 1d4 damage) 6. Glue! (fixed to surface for 1d4 rounds or STR). Roll this again and the traps just got a little bit more nasty (1d6 damage, longer duration, etc.).
19 Gluey fingers: How did they manage to steal this wand out of your pocket?! After every fight with a group of goblins, one of them and one random item of the characters possessions is missing. Roll this again and two (three, etc.) are missing.
20 Magical affinity: they saw a wizard do his stuff, now they gesticulate wildly and mumble strange words. There is a 5% chance per encounter they copy some spell they saw to half of the effect. Add 5% every time this comes up. The goblin managing to copy the spell, will be able to do so again with a 1 in 6 chance. After that, add +1 to the roll for every time he manages to do so (up to 5 in 6).
Basically goblins adapt pretty quick in any situation, but only up to a certain point. I'd say no more than 10 escalations per location, then they got what they want (mayhem and destruction) and are on the run. But they keep two of the 10 rolled advantages they got (plus the mutations extra). If a number did came up more than once, they keep only the advantage of the first roll. But if a tribe had the advantage to begin with, the next possible increase stays (and so forth). This way they could evolve with time.
Or just roll a number of times on the table to see what a random tribe of goblins might be made of. Works both ways.
Please let me know if you came to use this. Feedback would be much appreciated.