After that, somehow he is able to trick Ser Gilbert into trusting him and opening the gates, after which he is easily able to take the castle and slaughter the garrison. My thoughts: To get anywhere near Storm's End, he first has to attack the Tyrell force. Aegon doesn't know much about Storm's End. (everything) and surrounding it is a thick, high (30m), smooth wall. Storm's End consists of one huge, strong tower containing the granary, barracks, armoury. Mace Tyrell left Lord Rowan (Jaime thinks him an able man) with a token force to continue the siege. Stannis' uncle (Estermond) is also there and they have a garrison of 200 men.
Second in command is Lord Elwood, the one who yielded the castle to Stannis when the 1st in command died by shadowbaby.
The castle is held by Ser Gilbert Farring (former squire to Stannis). The situation: Storm's End is still loyal to Stannis. My question is: how will he do that? He insisted on leading himself, so the way he does it will tell a lot about what kind of person/leader he is/will be (aggresive, rash, wicked, smart, lucky.). If they take it, it would be a big accomplishment and everyone would see him as a serious contender in the Game of Thrones and a plausible Targaryen. As we know, Aegon and the GC have set their eyes on Storm's End.