All the others can be replaced with other Rank 4 Xyz Monsters
I could be wrong here, but I would be very happy playing three of this card in any B/R/X strategy, and especially so if I were playing with an aggressive slant to my deck
Rarity, condition, grading, market demand, and recent sales all play important roles in determining value
Lilah, Undefeated Slickshot Lilah, Undefeated Slickshot plots Slick Sequence for you, as well as Lightning Helix and Sacred Fire if you expand your colors
The card is so scarce that it barely has a stable market value since sales happen so rarely
It can be used for all of the same sorts of plays, but rather than adding mana, it can trigger lifegain, which can put you over the threshold for some effects, or just trigger putting +1/+1 counters on things