The increase from Gibeonite Trickery only lasts until the end of the battle.
Type: Evil Enh. • Brigade: Brown • Ability: 0 / 4 • Class: None • Special Ability: Each Hero in battle gains 0/4 and the battle immediately ends. Ability can not be interrupted or prevented. • Play As: Increase each Hero in battle 0/4 until the end of battle. Battle immediately ends. Cannot be negated. • Identifiers: OT, Depicts a Weapon • Verse: Joshua 9:3-5 • Availability: Patriarchs booster packs (Uncommon)
See also:
• Battle Immediately Ends
• Cannot be Negate
• Increase or Decrease Abilities
You'll notice the play as which clarifies how Gibeonite Trickery works. It's also categorized as an increase or decrease ability (http://www.redemptionreg.com/REG/default.htm?turl=generaldescription6.htm).
These cards increase or decrease the ability (strength and toughness) of characters in a prescribed way. The increase or decrease is a fixed number. Some cards may affect more than one character. The increase or decrease lasts until the end of the battle unless specified otherwise (i.e. end of turn). After the battle, the characters not discarded in battle return to the territory with their original ability. See Greater Worth for cards that increase at a variable rate, the rate dependent on other conditions.