Ilana asks Frank 'What lies in the shadow of the statue?'

Frank Lappidus makes it back to the Hydra island to immediately have one of the 316 survivors named Jed to come running towards him screaming his name. Jed tells Frank that Ilana and three others found guns and have taken control. Frank asks where they are and Jed just looks to the right.

Ilana and Bram are on the beach moving the same crate as earlier in the episode. It has AA823 on the side which includes two of the numbers, 8 and 23. As Frank approaches, they both pull guns on him. Ilana asks "What lies in the shadow of the statue?" Frank looks confused and asks "What?" Bram yells at him to answer the question. Ilana asks again and Frank says "I have no idea what.." and Ilana hits him in the head with the butt of a gun. Ilana tells Bram to "Get everyone else, tell them it's time." She also tells Bram to tie Frank up because he's coming with them. Frank passes out on the sand.

So who the hell are Ilana and these other people? What is in that crate and what do they have planned once they get to the main island? Also and most importantly, how do they know what lies in the shadow of the statue? Have they been to the island before?