The Japanese card of the day is an addition to Dark Irregulars' group of Psychics, the legion grade 3 Rigel. Dark Irregulars fans will be surprised to find that Rigel's legion mate is none other than Izaya, a promo card first revealed in June of last year. Rigel's Japanese release in G-BT03: Sovereign Star Dragon on May 29th will fall a week short of their card-of-the-day anniversary.
Rigel, Hadar and Izaya are actually all psychics of dust (Jin 塵 "impurity") but while Izaya's dust is sanded (Sajin 砂塵) and Hadar's is ashen, (Haijin 灰塵) Rigil's is winded (Fujin 風塵.) Rigil is the wind to Hadar's fire and Izaya's earth. His setup skill is one of the best in the clan; once per turn Rigel can soulblast a card with the same name as a unit on the vanguard circle to soulcharge five, putting him within range of Dark Irregulars' first soul benchmark and halfway to their second. Bear in mind that the key soul thresholds at this time are six, ten and fifteen soul--just by riding normally and using Rigel's skill you should have at least seven soul amassed, giving access to Flying Librarian and other six soul-required skills. Being in legion doubles the number of potential soulblast targets, making the skill not especially good for pre-legion setup and instead helping to brute force one's way to the benchmark for Rigel's other skill.
Rigel's soulcharge 5 should be taken into consideration alongside two other units, his mate Izaya and the grade 1 Doreen the Thruster. Both of these units get +3000 power when a card is placed into the soul during the main phase (Izaya only while the vanguard is in legion) meaning that with Rigel's soulcharge these units will get a total +15000 power. Doreen becomes a 21000-power booster and Izaya a 24000-power attacker, so that if both are lined up it forms a 45000 power lane. If you instead choose to divvy them up across multiple rows, you then have the option of two 30~31000 power attacks rather than a single big one.
Rigel's legion counterblast 2 is where the endgame comes into play. When he attacks the vanguard and you pay the cost, if there are ten or more cards in the soul you can retire two of your opponent's rearguards; and if there are fifteen or more cards in the soul, you can retire one more on top of that. Ten cards in soul is perfectly acceptable as a benchmark between stride turns with Kiskil-Lilla and the Abhorrent One, but the main obstacle to the last part of this skill is that if you've already reached the 15 soul mark before your turn begins then you're better off striding into the Abhorrent One to end the game. The only reason you would use Rigel's skill instead of the Abhorrent One's is if you've already run out of copies of the latter, or to avoid decking out via triple drive. These properties mean that a savvy opponent can also gain a great deal of information depending on your actions; if they are at four damage and you refuse to stride but clearly have the soul count and deck remaining to stride safely, then it becomes obvious that you don't have cards of the necessary grade in hand to stride with, and if they've been keeping track of your drive checks that lets them infer a great deal more about what you have at your disposal. Regardless, the simultaneous loss of three regards or six across two turns may be too crippling for the opponent to come back from long-term.
As for what grade 3 Rigel pairs with best, Charharlot Vampir is an option but using Hadar has certain benefits. It allows you to repeatedly cycle triggers into the deck with two different grade 3s, and each time you ride over an in-legion vanguard it builds two additional soul at a net expense of -1 to your card advantage. If your rearguard soulcharge options are limited in a particular game but you draw both units, you can perform legion with Hadar on one turn, then on the next turn ride Rigel, perform legion again and soulblast the Izaya from Hadar's legion to reach a high soul count without relying on grade 1 and 2 support units.