For version 2.0 onwards you will also need to install Roughly Enough IDs (whose modid is "jeid" and which is an update of Just Enough IDs).
This is the Triassic dimension. The portal block needed to get here and the biomes included are listed below. To open a portal click on it with the bone wand, which has been enchanted with the Enchantment of Time Reversal. The Enchantment of Time Reversal can be obtained from a Palaeobotanist villager, or as a rare chance on the crafting table. Note that the biomes in these dimensions are able to be extremely large, up to several thousand blocks across. Travelling 10 blocks in the overworld will move you 100 in a custom dimension though, and the main mod's config has an option to allow you to increase that if you felt the need. There are achievements for finding all biomes (biomes listed on the same line are regarded as equally valid for those achievements):
Triassic: Portal block: Dicroidium fremouwensis planks
- Triassic Deep Ocean
- Triassic Shallow Ocean
- Triassic Clam Beds
- Triassic Beach
- Triassic River
- Triassic Volcanic Islands / Triassic Pumice Beach
- Triassic Canyons and Creeks
- Triassic Rocky Desert
- Triassic Desert Dunes
- Triassic Desert Plateau
- Triassic Pleuromeia Beds
- Triassic Flooded Forest
- Triassic Dense Flooded Forest
- Triassic Cool Temperate Forest
- Triassic Cool Temperate Forest Crags
- Triassic Cool Temperate Forest Clearing
- Triassic Temperate Moss Meadow
- Triassic Mountains
- Triassic Warm Lakeland
- Triassic Warm Volcanic Hills
- Triassic Woodland
- Triassic Sphenopteris Uplands
- Triassic Polje
- Triassic Xeric Forest
- Triassic Xeric Scrubland
- Creeks (regarded as subversions of their surrounding biome and not counted towards biome-discovery achievements)