Not every contractor is a walking tactical weapon. Some eschew traditional flashy beam attacks, instead supplementing their magic with straightforward defensive combat ability. The guardian uses shields, and uses them well, as well as being able to single out foes and challenge them to one-on-one combat.
Challenge (Ex): At 1st level, the guardian gains the ability to challenge foes, as a cavalier of her level. The guardian may issue a challenge once at 1st level, and one additional time at 4th level and every three levels thereafter. This ability replaces beam.
Shield Expertise (Ex): At 2nd level, the guardian is proficient with tower shields and takes no penalties for using improvised shields. The guardian gains Shield Focus as a bonus feat. This ability replaces the guardian's 2nd-level perk.
Contract: If a guardian with the buster device contract spends a point from her buster device's divine pool to generate a beam attack, she instead issues a challenge. Guardians may not select the evolution contract.