The rules say:
Equipment spells have a range of “0-2”. Normally, a Mage will be casting equipment only on himself. But, if he wants to cast it on a friendly Mage (in a team game), or have a Spawnpoint such as Battle Forge cast the equipment on him, then the range requirement must be checked. You can cast equipment on an enemy Mage too, but you cannot cast equipment on a location that is already taken on that Mage. You may not have more than one equipment spell with the same name attached to your Mage at any time. Some equipment spells have an attack bar on them, and give your Mage a new attack he can perform. When the Mage makes an attack, he can choose to use an attack printed on an equipment card, instead of another attack he may have.
Setting aside for a moment why I'd want to do this...
In a mirror match between two Warlocks, if I cast Sectarus, Dark Rune Sword on my opponent (who has no other equipment in the weapon slot), can my opponent's Warlock make attacks with it? I control it, but it's attached to him, right?
Who chooses what spell to ready on Sectarus each turn?
If my opponent does attack with it, who decides if it casts a curse on the creature it damages?
Who controls those curses? Whose mana can it use?
The rules do say:
If you control a Familiar during the Planning Phase, you may select a spell for it to cast during the round.
and they imply that if you control the familiar it is "yours" and you control any spells cast by "your familiar".
I'm asking because of the potential interaction between Armor Ward and Steal Equipment discussed elsewhere.
Sectarus would prepare spells from your spell book and cast the prepared spell from your mana pool if need be. The opposing warlock could make attacks with the Sectarus since the equipment gives him an additional attack bar option. This is not "using" Sectarus because the opposing warlock is using an attack bar option given by Sectarus.
It's like putting bear strength on an opposing mage, he still gets melee +2 but does not "use" the enchantment since you used it to give him the ability.
This is cut and pasted from the rules:
"Important: If a creature has more than one attack bar,
you must choose only one of the attacks to use each
time you attack. If your Mage gains an attack from a
spell or piece of equipment, you must choose only one
of the attacks your Mage has available (including the
basic one listed on his ability card) when you attack."
You would control any curse that was cast from sectarus of course; and since the wording on Sectarus is "may cast" the choice is yours if it does cast at all