Mass Wyverns aren't that hard.
-If someone has lust, be undead and use gargs
funny that doesnt work, Gargs ****ing suck against wyverns. Especialy since wyverns do extra damage to them, with chain lightning and a few bats, gargs are history. 3 bats can wipe out any amount of gargoyles, and chain lightning deals mad damage.
-Rush them soooo bad beforehand that they cannot do it in the beginning
Burrows make rushing nearly impossible, except against retarded opponents. it takes only 7 minutes into the game to get enough wyverns to repel fiends attacks.
Death and Decay (assuming the enemy doesnt move or kill you when you cast it).
A level 6 hero spell on a second choice hero, that doesnt even damage air.... That is possibly the worst advice...
-FIENDS!!! (if they dont die)
Fiends collision size allows them to be picked off by wyverns, seeing as how web range is less than a wyverns attack range, wyverns pick of fiends easy. chainwave makes fiends unavailable to a serious undead player.