D-dragons are HYDRA dragon soldiers injected with D-virus or Dragon virus. It´s mixture of T, G, A and C-virus. For dragons these don´t cause any mutations unlike to humans. Staircase to the Sun or Ancestor Flower was blessing by the ancestors and grow only places that are blessed by them. They weren´t meant to be used by humans, only to admire. But Umbrella didn´t knew this and hell broke loose.
Dragons use flower´s abilities to boost themselves in combat temporalily, some ganining powers that were as strong as ancestors themselves, hence the name. Humans are called Punished Ones, dragons don´t call the viruses, viruses due those don´t affect them like viruses, rather like boost for combat.
T-virus/Tyrant virus: Enchanced strenght and speed, bigger size aswell.
G-virus/Golgotha virus: Regenerative powers and some specimen gain bony armoring.
A-virus/Animality virus: If D-dragon is put under lot of pressure and despair this virus will make it even stronger and faster, feral and brutal in order to protect itself. This virus is like Adrenaline rush but more animalistic.
C-virus/Chrysalid virus: This is strange one, D-dragon is able to breath out blue gas to cover their alliance to cocoon, allowing them to heal in peace. User can do it to themselves aswell. They too can use it to trap their enemies, and when cocoon opens they are dead.
Uroboros: Uroboros was added to make very lethal D-dragons, what already was deadly creature is now unstoppable weapon.
Notes:

• Stronger than average dragon.
• Faster than average dragon.
• Occasional specimen gain body armoring.
• Able to regenerate.
• Able to climb on surfaces and use its tongue as weapon. Sidenotes:
• They can´t surpass their leader Redhead even in packs.
• They still have all HYDRA soldier capabilities that were from their human form like talking and intelligence.
• They remain below Dovan volcano, only surfacing to big fights when their abilities are needed most.
• Effects of D-virus are temporary but last like 15 hours until they reverse back to normal dragon HYDRA soldier state. Notes of D-Uroboros dragons:
• Can use its many tendrils to catch its targets, impale them and re-attach its lost body parts.