mtg future sight booster box - BoosterBox | English Concluding the story of post Magic: Future Sight Booster [Spanish]

Though its physical appearance is definitely a factor in its price, the value of its effect is another reason why it's so sought after

[R][C] Flare: 20 damage

The actual math behind the function is very difficult and so I wouldn't want to do it by hand

Even amongst the monsters, it is very rare to see this kind of protection given permanently and unconditionally (the easiest monster to summon with this protection is the level 10 blackwing synchro Blackwing Full Armor Master which prevents him from getting his own attack boosted by the effects of other Blackwings)

Sometimes that SR slot is a Special Art Rare (SAR)