Many of the Duel Links Skills are bugged, here is some that I’ve checked and tested.
Shell of a Ghost
The skill simply just does not work. Meeting the requirements and all, You are still not allowed to activate the skill.
When you activate the skill to create a Vanilla BEWD into Alternative White Dragon, The Alternative is still considered a Vanilla BEWD. When added back to the hand with White Stone, If you have the full requirements to reveal BEWD to SS Alternative. The game does not allow it as Alternative is still a Vanilla in the games eyes.
While the skill provides the Buff/Debuff as Umi describes, the card Sea Stealth Attack does not recognize Mystic Depths as Umi. As such SSA does not activate to play the Mystic Depths from the GY onto the field. It needs to be seperated from the Speed Duels Version and played like the Skill Harpies Hunting Ground.
The skill does not act as a field spell in the hand, so you can not activate it to become a Mountain Field Spell. Unlike its counter part, Harpies Hunting Ground. HHG has no issues as its plays a HHG outside of the deck as a real field spell. It needs to be seperated from the Speed Duels Version and played like the Skill Harpies Hunting Ground.
Activating Restart to get a new hand, My draw was suppose to be skipped but it did not and I drew a card like normal.
No Mortal Can Resist
The skill is not a once per duel, I clearly showed that I activated it the turn before. Still was able to activate NMCR again, In addition I can activate NMCR as many times as I want during the same turn. Activate once or even twelve times in the same turn.
Related Screenshots of the Bugs ingame are shown here: Duel Links Bugs - Album on Imgur
This is only the minimum of what I’ve noticed and looked into.