Reach refers to the ability to finish off a wounded opponent, even once you've lost your initial tempo advantage
Once you've got Selvala tapping for at least six mana (this can happen as early as turn three), you can pair her with cards like Wirewood Symbiote + a mana dork, Umbral Mantle or Staff of Domination that untap her for a portion of the mana she makes
Meanwhile, mythic Mystical Archives are a bit worse
Firstly, it gives us another instance of lifelink on our instants and sorceries, something we saw a while back with Firesong and Sunspeaker in Dominaria
NameSetBuySellChanceValueCart Swords to Plowshares (Borderless)1 : 6400.002 Ledger Shredder (Borderless)1 : 6400.002 Secluded Courtyard (Borderless)1 : 6400.001 Rat Colony (Borderless)1 : 6400.001 Relentless Rats (Borderless)1 : 6400.001 Frogmite (Borderless)1 : 6400.001 Toski, Bearer of Secrets (Borderless)1 : 6400.0007 Kindred Charge (Borderless)1 : 6400.0005 Sylvan Tutor (Borderless)1 : 6400.0005 Sword of Fire and Ice (Borderless)1 : 6400.0001
You can also find these four colorful neon ink foil Traveling Chocobo cardspink, green, yellow, and bluein all languages of Collector Boosters