I have been updating tags for the Cube.

Burn - is for spells that can specifically deal damage to a player. If a spell can only hurt creatures, the tag is not applied.

Kill - is for spells that can destroy a creature by any means. Obviously, Black creature removal effects make up the majority, but also Red spells that deal damage to only creatures. Spells that cause -X/-X are also tagged with this.

Tricks - is for spells that will allow a creature to survive combat. So, obviously green BOOSTing spells go here, but also -X/-X spells are also included, and white spells that prevent damage, and other combat tricks. (including the unremarkable Blue -X/-0 cards) Tap effects are not tagged with this because they can't be applied in combat anymore.

Pacifism - is for those enchantments that stop creatures from attacking / blocking, or O-Ring like effects that will remove a creature until the Enchantment leaves the field.

Freeze - is for spells that tap down creatures.