Melt Virus

Melt Virus is a poison used by Meltlilith.
Usually administered via injection. The poison works from the inside to melt the mind and body of the victim. It gives great pleasure to the victim while they are liquified alive.

Meltlilith uses the liquefied victim in two ways:

  1. She drains them for EXP.
  2. She redesigns them as a “Virus” to suit her taste.

Number 1 is exactly as written. The liquefied victim is absorbed into Meltlilith to supplement her EXP.
In chapter five, Shinji is shrunk down to nano size because he was hit by the combination of both 1 and 2.
But Elizabeth was only redesigned by the virus to be used as a boss character.
If Meltlilith were to break her own “Level Cap” and were to infinitely increase her level, the scale and potential of Melt Virus would also increase infinitely. In any case, as the name “Melt Virus” implies, everything would be melted and swallowed up into a massive demonic sea… just like one of those blob monsters in a cheap B-grade movie that melts everything.

Fate/EXTRA Material: Encyclopedia of Fate/EXTRA