Tourmaline

Tourmaline is a special gem created by combining Perfect Aquamarine, Flawless Opal, flawed Aquamarine and flawed Emerald. It is the only special gem to use four gems in its construction.

The gem serves the function of above-average single-target damage, especially when aided by stunning gems, and dwarf armour reduction. As in post-40 survival rounds full (-14) reduction of armor roughly doubles the damage done, this is very helpful for time score.

Although it has higher raw stats, cyan damage on violet-weak land waves takes 1* multiplier, making it likely lose in kills to well-placed Gold or Dark Emerald.

Tourmaline can be upgraded to Paraiba Tourmaline for 350 gold, which is all-around upgrade for the greatest monetary upgrade price. A rough estimate of the 93 armor-reduction radius can be gotten via flawless diamond.

Like with Ancient Blood Stone, the internal mana caps at 10. Unlike with Blood Stone's, Perfect Opal-boosted Paraiba Tourmaline will use up mana slightly faster than it regenerates, giving it easily-estimated 100 DPS that isn't affected by colour, kills or opals.