This is one of the few cards in the game that has real game-breaking potential. This is due to the fact that from a value perspective allies as a card type outclass every other card type in the game, and this card allows you to cheat in allies ignoring their cost. Due to this you are going to want to deck-build around high cost or high impact allies such as: Giant Man, Beta Ray Bill, Nick Fury to name a few.
Let’s evaluate those allies based on the best things they can do, ignoring their ability to block (except for Nick). If Summoning Spell hits Giant Man you’ve spent 2 for 8 damage and 4 thwart. If you hit Nick you’ve spent 2 to draw 3, thwart 2, and block. If you hit Beta Ray Bill you’ve spent 2 for 12 damage and 8 potential threat removal. Swinging Web Kick is considered to be a standard for damage comparison at 3-cost 8 damage. Not particularly impressive compared to what allies can do.
This card is trait-locked and limited to 1 copy as an attempt to gate some of its power, but 3 out of the 4 Mystic Heroes all have methods of fishing this card back out of the discard pile: Sanctum, Quantum Magic, and Magik’s alter ego ability.
During deck piloting you will want to be actively tracking what allies are left in your deck, but that’s a small chore for the results this card yields. Assuming you’ve deck built correctly, playing this card will be the best thing you can do almost every turn.