Glacius Tria is a charm used offensively in duelling to freeze a target enemy. It is the most effective version of Glacius, being more powerful than Glacius Uno and Glacius Duo.

Glacius Tria is presumably mentioned or referenced because of its contemporary, Glacius Uno, in The Standard Book of Spells, Grade 3, published by Miranda Goshawk. With this assumtion, it is likely that it will also be acknowledged in the Glacius spellbook, which quite obviously contains data and instructions on the Glacius charm, and perhaps its more advanced counterparts. Even with this, Glacius Tria still remains to seem seldom used, and information along with utilisation have prevailed to a dubious archetype.