None. A summoned spirit has a damage threshold equal to its summoner's heal value; any attack which deals more damage than that threshold banishes it back to the spirit world until re-summoned, while any attack which deals less damage is ignored. When a spirit you control is banished due to damage, you take psychic damage equal to your heal value.
8. The spirit ignores difficult and treacherous terrain.
Armor: 13 + half caster's level.
Reflex: 13 + half caster's level.
Fortitude: 12 + half caster's level.
Will: 13 + half caster's level.
You may command the spirit to perform a Wolf's Lunge or Wolf's Howl Attack as Rank 1 trances, using your Skill and ability modifiers.
You charge the target, dealing 1d6 + your [ magic damage bonus ] slashing damage. The target is grabbed and knocked prone. Until the end of your next turn, your allies gain a bonus to attack and damage vs. the target equal to your Constitution modifier.