Fling

Description
Cast the spell in your other spell slot, and Backfire it.

Strategy and Synergy
Fling can allow you to use high mana spells such as Fimbulveter without paying the usual mana cost, which is very helpful for decks that have low maximum mana and/or mana regeneration.

The downside of backfiring your spell can be mitigated by using it on spells that normally would consume theirselves anyway, or simply having a broad host of powerful spells.

Fling can also be used to thin your deck of less useful spells that you'd rather not draw again, making it great for composing combinations of powerful abilities to repeatedly shuffle through.

Fling is especially good for spells that have been enhanced with upgrades such as D (Double) or O (Overload), allowing you to avoid or make redundant their downsides while still benefiting from the doubling effect.

Fling can be used last out of your deck to avoid backfiring another spell, great for situations where you've already backfired everything you want to.

Fling's backfire effect can be something of a liability for decks that heavily lean on repeated use of one powerful card or those that want to cycle through a lot of powerful effects quickly and reshuffle frequently.

Trivia
Fling may be a reference to the Magic: The Gathering spell of the same name, which requires the sacrifice of a creature to "fling" it at a target, similar to Fling or the Pokemon move of the same name, which sports a similar effect.