Swamp drake occasionally does no damage to the twilight abbomination. Kapo confirmed this in the forums and I have seen this happen to an other player via discord stream.
In the replay attached to this post it happens at 20.05 min on the T2 monument of the right side player. After the swamp drake uses its ability all of them do not deal any damage, after the thunderstorm has been played everything seems to be fine again until the Abo starts attacking the drakes.
Kapo though it had something to do with the cc, wich might be possible, but I'm 90% sure, that on the discord stream the palyer just straight up attacked the abomination on behind enemie lines and they didn't deal any damage for 3 to 4 attaks each. If you also need this replay, I can ask him or/and contact a gamemaster and try to search the replay on the server. 2022-06-10_19-45-41_NightmareShard_diff3_s51276_arabika_Mocaak_time_0_22_45.1_v258.pmv