Every Timekeeper has a chance to get a 6-star Psychube (equivalent to weapons) by just logging in to the game for a few days. Since it's a precious item, you should choose carefully depending on what characters you currently have so as to not waste this opportunity.
How to get a Carrierwave Carrier
Carrierwave Carrier is available from 8 Daily Letters Event where you need to log in to the game for 5 days. The event itself is 8 days long to get Dikke (a 5-star character), but you can get Carrierwave Carrier on the 5th day.
Once you obtain the item, go to Warehouse from the home screen, under Consumables to see and use the Carrierwave Carrier. There are 7 6-star Psychubes in the carrier and you can only choose one of them.
Recommended Psychube for Carrierwave Carrier
*Remember that the rating below is not based on the best to worst Psychubes, but the one you should get from the Carrierwave Carrier. All of them are 6-star Psychubes, so none of them can be useless.
・Increases Crit Rate for the wielder, and when a critical hit occurs when attacking a single target, the Critical Damage increases.
・Only for characters with any single-target spell (especially DPS).
Brave New World
・Increase the power of Ultimate and even more boost for the next Incantation (normal spell) after the Ultimate.
・Can be equipped on both DPS or secondary DPS.
・Incantation: It's literally your 2 normal spell cards, not the Ultimate.
Her Second Life
・Increase attacks and recover HP for all allies when using mass Ultimate.
・Only for characters with mass Ultimate (attack multiple enemies, not a single target).
・Mass attack abilities: Attack the chosen target and then choose the rest of the targets at random
Blasphemer of Night
・Increase normal spell attacks, and damage dealt increases when attacking targets that have 2 or more "Neg Status"
・Neg Status: Use Debuff spells to inflict any negative status on enemies. You can check whether enemies have Neg status or not during combat by tapping on them.
That Inquisitive Dear
・Can recover a single ally with low HP when using normal debuff spells. In a way, a bit similar to APPLe's spell as it can only heal an ally with the lowest HP.
・High requirement but low effect; use normal debuff Incantation and can only heal a single ally with the lowest HP. Characters who can't debuff an enemy can't use this Psychube.
・Increase normal spell attacks, and Ultimate power increases with each enemy defeated (stack up to 4 times)
・Suitable only for stages with lots of enemies/waves, not for boss fights.
His Bounden Duty
・Good damage bonus, and recovers own HP for each enemy defeated.
・Can only recover health for the carrier, and that is if the carrier is the one who dealt the finishing blow. If you miss that single window, you're gonna waste this ability. Another Psychube that is more suitable for stages with lots of enemies/waves instead of boss fights.
Aside from the effect of each Psychube (which has been discussed above), it's also important to check first what characters are in your main team, and which ones still don't have any good Psychubes. You can check our guide below for Best Psychubes for Every Character.