Both the Rego Terram spells "The Unseen Arm" and "The Unseen Porter" seem to be spells to produce what we would call telekinesis, with a couple of limitations. If you want to move something that is not covered Terram, then the spell is ReTe with appropriate requisite, but no added increase in spell level.
The limitations are :-
a) target is unliving
b) cannot oppose intentional resistance (eg held in a persons hand)
I think I understand a), if the target is living it would overwhelmingly (I presume is the correct adverb) a part of another Form (Corpus or Animal, or Herbem) (or Vim for Demons/Angels) (or possibly other Forms for particular supernatural creatures).
But why the second limitation "cannot oppose intentional resistance"?
"The Unseen Porter" ReTe10 acts as if it has Strength of 5. Surely it could pull a metal sword from somebody's fleshy grip?
What would I need to add to the spell design to oppose intentional resistance?
Also "The Unseen Porter" says it can't lift anything more than 6 feet above the ground (a limitation that "The Unseen Arm" is not listed as having). This is annoying when trying to lift things (eg bricks or stone blocks) to the top of a tower. Or drop a rock from a great height upon someone.
What sort of modifier in spell design is needed to get past the 6 foot limit?
I regard the 6 foot limit in The Unseen Porter as a spell issue (to me a flaw, but ymmv).
ReTe Level 3: Move dirt in a highly unnatural fashion: +1 for stone, +2 Voice, +1 Conc - Levitate an individual object as dense as stone to any height, up to about 15 paces*. The object does not move laterally from the effect of this spell, but can be blown aside by a wind strong enough to shift the object's weight**. The object moves at about a walking speed.***
*Based on the rough Voice distance guideline. The caster is essentially defining a column the object is lifted in, and the column is limited to Voice range; I suppose a shouting mage could raise the object up to 50 paces on a still day.
**The object is not weightless or massless.
*** Slow by modern elevator/lift standards.
In Legend of Hermes (p123), the base effect used for the Flying Castle is base effect: 3. And it does not fly only a few foot over the ground: it is a flying castle.
So take the base 3 to move the target within the spell range, and ignore other limitations. Don't forget the modifier if it is anything else than dirt or sand.
Frequently, the Rego Corpus guideline are used as base for TP spell, so to take something that is bound, you can also consider as guideline: ReCo 10, transport the target instantly up to 5 paces. As long as it is not "welded" to an anchor, you should be able to get anything you want, whether it is held by hands or with a rope or a chain. Keep in mind that you need to see the target, knowing that it is there is not enough (like to steal a key in a pocket or held by a chain around a neck, but under a shirt).
Teleporting or ripping a "Part" should probably be considered according to the damage it is dealing.