No, there's no need to panic. If we're talking about a game against the computer, then everything you said is correct. But a player who understands the game won't let you "hit-and-run" their entire army, and it's not that easy to quickly eliminate 3-4 thousand skeletons. Even without health-boosting artifacts, a skeleton has 6 HP, which means that's 18-24 thousand HP for the army. Even for a powerful explosion, that's at least 10-15 rounds of attacks. You'd have to be a really bad player to position yourself right next to the castle and get caught in those 10 rounds, and 2-3 rounds won't do much. Sure, you might destroy 300-600 skeletons, but that won't solve the problem. Of course, all of the above applies to players of roughly equal strength. In this case, I wouldn't dare play any race against Galtran, especially in the 4th month. And the lack of water magic isn't critical for the Necromancer; experience gain acceleration and counterstrike, combined with a stack of 3-4 hundred Vampires and 3-4 thousand skeletons, along with other Necromancer units, will overwhelm any opponent. Note that 3-4 thousand skeletons is the minimum Galtran will have; on a random XL map, he'll have significantly more.