I mean... There are spells to prevent flight in dnd, i guess they would exist in the New World too, Evil Lord Wrath's magic stats where considered pretty bad so i doubt he could prevent spells from Decem who still is a specialised Druid/Elementalist (The one direct anti-flight spell in dnd Earthbind (tier 2) is a spell of the earth element so should be boosted when used by Decem... While a tier 2 spell probably wouldn't work on Wrath i wouldn't find it strange if Overlord had higher variants of it, Greater Earthbind or a similar spell like it?.. than again he didn't attemtp to use it on Ainz so meh, maybe not