There was a crack, and a moment later, Lyra appeared under a dense canopy which blocked all but the strongest rays of sunlight. She didn't bother with a mask or robe. The curious foliage of the Forbidden Forest would make wearing a robe a hazard, and she was too far in for concealing her identity to be necessary.
Immediately, Lyra pulled her wand from its holster and performed the point me spell. Then, sure she had her directions right, she set off in the direction of the lake. It wasn't long before the land began to get grassy, and she knew she was in the place Lucius had spoken of. The way in was literally through one of the huge rocks in front of her, but that wasn't why Lyra was here. Her wards would begin long before anyone could even see this clearing.
She walked through the forest, toward the school this time, and stopped when she could no longer see the clearing, but couldn't yet see Hogwarts. The first charms were simple, common things. They were used often by St Mungos, and indeed, a variation protected Hogwarts itself, so her use ought to go undetected by both staff and students.
On the other side of the, well, call it a hideout, the wards got stronger. Every hiding place needed a back door and this one was no different. Unfortunately, this back door came out unnervingly near an acromantula nest, so she made it one way only.
Closer to the front entrance, Lyra's wards gave way to alarm spells. If, by some chance, the staff of Hogwarts, the Auror Department, or the Order of the Phoenix did attempt to attack them here, they would need the time to not only clear out, but to move the hostages as well.
Done with the outside, Lyra moved to the entrance, tapped it with her wand and said the appropriate incantation. It stood and moved aside to allow her access to a hole directly below it.
She bowed and thanked it before dropping into the cave below. Sure, some things felt stupid, but some things were also better than being pummelled to death by a standing stone.
The cave was dimly lit by a phosphorescence and Lyra wondered how long it had been since anyone had been down here. Not that long, she remembered, for Lucius had been here quite recently.
She began to walk through the maze of underground tunnels, adding interior defences to places of structural fragility.
((Adult Death Eaters may begin to arrive now))