When you quest with a character that has the Support keyword, you can add that Support characters strength to any character you choose other than the Support character
Take yesterdays deck when I ran this with a bunch of zero drop artifact creatures and used Paradoxical Outcome to bounce them, play them again with new zero drop cards we drew, and keep it going to build a giant count of cards played in order to kill everyone at the table with the Reservoir
In terms of support, your deck should likely include as less non-Character cards as possible
In white you have access to Intangible Virtue to buff your board, Jazal Goldmane to overrun and Sephara Skys Blade to make your entire board indestructible
Repeatable engines One-shot blink spells are fine for protection and spot value
10s make a meaningful impact on any game, especially when playing from behind, and theyre extremely tough to beat