Force Athame (Sp)
At 2nd level, a spellblade magus can sacrifice a prepared magus spell of 1st level or higher as a swift action to create a dagger of force in his off hand. The athame lasts for 1 minute or until dismissed, has an enhancement bonus on attack and damage rolls equal to the level of the spell sacrificed (maximum +5), and is considered a weapon the spellblade is holding for purposes of his arcane pool feature (using the pool to add abilities to a held weapon applies to the magus’s physical weapon and to the athame for no additional cost). The athame acts as a dagger, but the hand holding it is still considered free for the purpose of casting spells and delivering touch attacks. The magus can use the athame as if he were fighting with two weapons, or can use that hand to cast spells as part of the spell combat class ability (but not both in the same round). Attacks with the athame are force attacks and deal force damage.
This ability replaces the spellstrike class feature.
A Spellblade would only deal 1/2 strength damage with their athame even if its the only weapon they are wielding (no TWF) because it is stuck in their off hand, correct?
Off hands only exist while TWFing, i.e., a full attack where additional attacks beyond the standard iterative attacks are made.
Spellblade makes the assumption the magus is already holding a weapon, but makes no requirement that the magus actually do so.