Rift challenges are short instances that have you work your way through a series of monsters to fight an end boss that gives you some decent starter gear for new players.
Starting at base level 20 your first rift challenge unlocks from the instance menu. Then tap More > Instances. On the left side, the top option in the list is Rift. If you don't see a list of instances like the below example then click the down where the red circle is below to bring up a list of all the rift instances. Select the one you want to run, the difficulty to run it at, then challenge this instance.
Accessing Instances
Rift Challenge Options
Each rift is a six man dungeon that pit you against three waves of enemies. Sometimes you face these waves as you progress through the stage, while others just send waves after you. After each wave a set of three cards will appear and you get to choose one that provides you with a buff for the rest of the run. After the final wave and boss are defeated a large chest appears that gives you base exp, job exp, zeny, materials, and with luck some new armor.
Harder difficulties are unlocked as you clear them so you'll have to finish the Novice version to access Adventure, etc. Higher difficulties offer better rewards such as more exp, and Brilliant gear, better versions of the armor that drops from Novice difficulty. This gear rolls random stat augments and is actually quite strong and it appears as if the gear can even drop with refines already on it.
New players should definitely spend their CT here to obtain some powerful augmented equipment to save some zeny while leveling.
Example of card selection between waves
Ring from Novice Difficulty
Ring from Higher Difficulty
Starting at base level 20 you can do Eddga's Roar but more challenges will unlock as your level increases. Higher level stages also drop better gear and higher difficulties of that stage drop higher quality gear. Here is a list of stages and their corresponding drops:
Eddga's Roar (lv 20) - Level 20 Gear
Strouf's Storm (lv 40) - Level 20 Gear
Morroc Shadow (lv 60) - Level 60 Gear
Seal under Sakura (lv80) - Level 60 Gear
Moonlit Rendezvous (lv 100) - Level 100 Gear
Turtle Island Watch (lv 110) - Tier 5 Upgrade Materials*
Divine Tree Defense (lv 120) - Level 120 Gear
Farewell, old Friends (lv 130) - Level 120 Gear
Othershore Showdown (lv140) - Level 120 Gear
Summer Showdown (lv150) - Ancient Equipment, Comodo Ancient Equipment Materials
Den of Calamity (lv160) - Ancient Equipment, Royal Hunting Grounds Ancient Equipment Materials
Once you clear a time rift dungeon for the first time you’ll be able to instant complete it from the instance screen. Click on the More > Instance button. Then select the instance and difficulty that you want to instantly complete. Click on the Raid button and it will prompt you to proceed. This will consume 60 minutes of combat time but instantly clear the instance
You will always use 60 minutes of combat time anytime you clear a rift challenge so raid just makes re-running instances easy by skipping the process entirely at no additional cost.
Location of the "Raid" feature
Note that the first three clears per day have an increased chance to give gear so don't continue to spam this more than three times a day if you're looking for augmented gear, wait until the next day
Once you reach the level 120 instances you can socket and safe refine using Wasteland Ember, a material created using Wasteland materials farmed in areas outside of Wasteland such as Sunset Beach. You likely don't have many of these materials as they don't drop in the areas that you've been farming to grow your Yggdrasil tree but may want to branch out to these other spots once you can so you can use those materials to upgrade your Wasteland Ancient Equipment.
You can also craft this gear, including the Brilliant versions which come with a random augment. This uses both Yggdrasil Spirit Tree materials and Louyang area materials but this allows you to create a whole bunch at once to roll for augments on a specific piece of gear so this may be a great option if you're looking for a specific upgrade.
For more on this type of equipment visit the Ancient Equipment page.