The two of them will be a while figuring out how this actually works.

Eventually, they are satisfied. Lhín can now communicate with Tencednil as if she was speaking. No actual sounds seem to change, and if Tencednil replays the exact same sounds (at least as far as she can manage) on a Ghost Sound, she can't understand any of it. It can't be silent, but anything loud enough for Tencednil to hear is interpretable, even if she's looking away from Lhín and is playing the same sounds with an illusion.

 It's a useful ability to have, but it doesn't open up too many options. It just makes everything much more convenient.

From there... well, she has at least five second circle spells a day, so using up one learning what her spell actually does is good. She probably has six now, but this might just be a delayed spell coming in, so best not to assume. This spell seems to want a touched target, or it could be pushed inwards at herself. Lhín is a familiar, though, so... She pushes it inwards along the bond, tapping Lhín as she does.

Lhín vanishes from sight!

<Are you still there?>

They can communicate without her being visible! As of just now! Maybe this will be a more useful ability. 

"Yes! But I can't see me!"

Some sort of invisibility, then. The Mantis definitely showed how powerful even restricted invisibility could be. This is probably the normal sort, but she should check. 

<Try moving fast, and then hitting the table.>

Zoom in a circle! She can't really go at full speed in here, but she can go very quickly! Zoom zoom zoom!

Tencednil can sort of feel the air move. She hears a soft whooshing sound but can't pinpoint where it's coming from.

It's not too easy to break, then. It would be rather ineffective if it broke this easily, but it could happen. Sorcerers probably don't always get particularly useful spells? Wizards definitely design bad spells sometimes, at least. Probably that can also happen to sorcerers. 

Anyway, there's another step.

Lhín has had enough zooming for now. Hello table, how would you like a shadow running into you at full speed? ...a very small shadow, which probably will not hurt very much if at all. But still.

A loud crash echoes across the room! Lhín slams into the table, which vibrates as she bounces off. Tencednil still can't see her.

Hitting things doesn't break this? Is that standard for wizard Invisibility? Hmmm.

<Hit me, but lightly. Minor bruises only.> She holds out a hand.

Smack! Hitting a stationary target is easy, and she's not strong enough to consistently leave a real mark when she is trying. When she isn't, a quick-healing bruise is inevitable.

Lhín's invisibility breaks as she flings herself at Tencednil.

As expected! (Also ow.) So that's a pretty much normal Invisibility, which means it should last a tenth as long as her lasting cantrips. That would be... probably four to five minutes? That's still not certain, but it's a good estimate for now.

Evocations, especially ones that target a creature or an area, are mostly painful. This might not be, but she should wait until this evening to test it, in case it makes Lhín vanish. She has a few guesses for what it could be, but they're only guesses. Unless she needs a spell resisted by physicality, she will hold off on using it until tomorrow when she's had a chance to test.

Any letters today? She'll pick up a bit of ink on the way, because she will send at least one letter today (and Lhín has the appropriate indents).

The Bank has no mail for her at this time.

She woke up late for a human, as usual, and she needs to be prepared by the time the Blessing comes around. She won't be writing any letters before her guard shift. To the Citadel.