Theodore was happy to see his allies moving to fulfil a similar plan, everyone seemingly wanting to strike at the behemoth at the top of the stairs as soon as possible. Before he could get a move on himself, he did notice that one of his companions was getting swarmed by the shadows, many of them failing to even scratch the abjurer through his magical protection, but nevertheless some of them seemed to manage said feat. Before the ranger got a move on, he yelled at Haemar: "Do you need any help with that?"

The reply came back negative, which in turn only had Theodore raise a thumbs up in response. It was both a sign of understanding and wishing of good luck, but he didn't keep it up for too long. He had an opponent to assault. The big thing had already tossed one of the balls it had been forming, so it was not quite as destructive as he had feared. He'd still rather avoid taking a direct hit from that if possible, but all he could currently wish for was for the giant shadow to not pay too much attention to him.

He climbed the stairs for about twenty feet, remaining slightly behind the front line his allies had formed, all the while cranking the reloading handle on his weapon. Had it not been crank operated, there was no way he could have shot it as often as he did, that much he had to admit. He raised his right hand before his face, pointing his forefinger and middle finger towards his eyes, then at what he could only assume were the leviathan's. "Marked for the kill", he declared mostly to himself as he placed another bolt onto his crossbow.

Trusting in the abilities and judgement of his allies, all he had to do was hit his shot. And that he seemingly did, with the bolt flying straight at his mark. By his own judgement, it did not seem that effective of a shot, but it was a definite hit nonetheless. At worst, this would turn into a death by thousand cuts... all that worried him about it was that they might not have the time to execute that tactic.

[hider=Effects&Rolls]
Theodore climbs up the stairs for about 20 feet, staying behind the obvious and recently attacked front line.
Sticking to the plan, he casts [i]Hunter's Mark[/i] on the Dark Leviathan, beginning concentration on the spell. He now deals an extra 1d6 damage on hit weapon attacks and has advantage on WIS(Perception) and WIS(Survival) checks to find it. The latter effect will likely be tremendously useful.
Having done that, he shoots his crossbow at the marked Leviathan, hitting the target on a roll of [url=https://www.roleplayerguild.com/rolls/2459]24[/url]. The attack (with the additional Hunter's Mark damage included) deals [url=https://www.roleplayerguild.com/rolls/2460]7[/url] damage.
[/hider]