It's trivial to cast it for 1-2 mana most of the time, and if you're the one casting it, you can set up combos with cards like Boros Reckoner or Stuffy Doll, hitting someone for 13 right away
This implementation went over well (making the mechanic historic) and created what we now call batching
As an added wrinkle, there are also two editions of each precon - normal and collector
This card is high on the fun scale, especially if the instant or sorcery cards that are exiled represent a vast difference in power and game effect
Like most Magic: The Gathering cards, the value of Alliance of Arms depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (The List)
Reprints of this nature include Scion of the Ur-Dragon, Lightning Greaves, Kindred Discovery, Elemental Bond, Dragon Tempest and more