The best replacement for serpent is snake.

The best alternatives to serpent are rated as following:
★★★★★  snake
★★★  aes
★★★  mugen
★★★  twofish
★  satan
★  pegasus
★  rijndael
★  vx6-7
★  dragonhawk
★  elephant
★  flame libra
  pulsar c
  storm pegasus
  kyosho
  vx6
  vx6 7
  rock aries
  dark wolf
  dark bull
  libra beyblade
  l drago

Your alternative for serpent is not listed? Suggest!
Speaking about serpent, one probably shouldn't forget about eve.

Other search terms related to serpent and their ratings are:
★★★★★ eve
You have in mind a companion for serpent and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of serpent in all years. Click on graph for more.
serpent
snake
aes