Some spells from the time of Saviors of Kamigawa can splice onto arcane spells, or cared about the spell type
Omos low-power stat line makes it a curious choice for an attack trigger, but its fairly bulky toughness makes it clear that the main point of this Creature attacking is placing counters, not dealing damage
Archmages Charm is extremely pushed, a solid permission spell, a good way to build card advantage for hitting land drops, and a fantastic tool against Deaths Shadow, Wild Nacatl, Goblin Guide, Pyxis of Pandemonium, Champion of the Parish, Aether Vial, Delver of Secrets, Hardened Scales, Amulet of Vigor, Benthic Biomancer, Glistener Elf, Noble Hierarch, Viscera Seer, and sometimes even Hexdrinker (just to mention a few)
Table of Contents show #49
In a format where value trades matter, Selenia gives you more options and more breathing room to trade up into your opponents creatures while protecting yourself from counterattacks