This ability is written absorb X. If a creature with absorb would be dealt damage, X of that damage is prevented. This ability appears on a single timeshifted creature from Future Sight, Lymph Sliver. Older cards with this ability were not changed to grant absorb.
This one is pretty straightforward, works alot like armor in some other games or damage reduction in DnD. It allows something to be tougher without adding more health to over-come. It also encourages fewer larger strikes over a multitude of tiny strikes.
This sort of thing if applied to an avatar you control could lead to feeling very powerful when wading through enemies. This however could lead to things being too easy as you wade through things unharmed. In order to add some skill to using this absorption but still have the enjoyment of immunity aspect, I am going to take some inspiration from Ikaruga.
Basically you have a variety of damage shield abilities keyed to specific types of damage, and the type of damage you deal would be the same as what you absorb.
So you could be safe from a fire elemental if you had a fire shield, but if you wanted to kill it quickly you would use a water/ice shield instead.