When running an open sandbox game, having good random encounter charts at your disposal is a must. I tend toward finding or making terrain based charts and then having an additional chart of “special encounters”. These encounters can happen in any environment and exist primarily to reinforce the themes, mood and atmosphere of the sandbox. in the case of The Return to the Isle of Dread, the point is to remind players that the Isle is a weird nexus of worlds and not at all safe.
The following chart is a little bit gonzo, and that is intentional. The Isle is a little bit gonzo, blurring genre lines and serving up some wicked wonder. It will probably see a little bit of modification before TotalCon rolls around, but you can see what the intent is.
d20
01: A tribe of 4d4+4 goblins living inside an animated T-Rex skeleton led by a bugbear witch.
02: A circle of severed heads on spears babble madly as per gibbering mouther. Bodies and loot in circle.
03: Mad explorers set trap gauntlet to catch a meal: spiked log, falling stones, snare over spiked pit.
04:Human barbarian and 1d6+2 awakened apes stalk area, killing hunters/tomb robbers & aiding innocents.
05:Haunted camp. Spectral explorers replay fight over treasure nightly. One can be traced to the gold.
06:Tree grows melon sized plums. Max any HD spent when consumed during short rest. Last 1d4 days.
07:4d6+6 draconians think they’re on Krynn and await orders from Highlord in a makeshift fortress.
08:Tree looks like the one with healing plums. Those aren’t plums: they’re 2d4+2 giant spiders.
09: Village of 5d4+10 phanaton is plaguestruck and needs help. 2d4 die/day until village is gone.
10:2d6+4 slavers have of 3d6 slaves in tow. Freed slaves repay kindness with secret knowledge.
11:Goblins! 2d4+4 ride pig size triceratops. Peaceful unless provoked. Other goblins hunt them.
12:Something slithers in an ancient yuan ti shrine nearby. 1d4+1 abominations stalk the PCs.
13:Allosaur nest with 1d6+2 eggs. Mother and father return in 5d6 minutes and will attack.
14:Couatl guards a magical fountain. Drink with permission 24 hour bless; without 24 hour bane no save.
15:Waterfall hides cave with treasure inside guarded by specter of original cursed tomb raider.
16:Small ruined tower inhabited only by shadow demon still trapped in magic circle and willing to bargain.
17:Bones of a massive dinosaur 500 feet long with dire wolf den (2d4) in the skull.
18:Zombie herd (2d6+6) wanders aimlessly. On death a necrotic worm escapes brain.
19:Fungal grove. If touched emit cloud of spores. DC 10 Con save or sleep 1d4 days. Roll encounters!
20:Ancient shaft 2d4x10’ deep. DC 12 Dex save to avoid. Treasure hoard at bottom CR 1d4+1.
I.E. 