Fire Emblem: The Sword of Seal (Import) Tips

Triangle attacks
Triangle attacks are attacks which ensure a critical hit aka boosting the hit and critical rate to 100% for one attack.

There are two different triangle attacks in this game, one involving all three pegasus knights, and the other involving all three Ostian armour knights.

To perform a triangle attack, position two of those three pegasus knights or armour knights around one enemy. Then, take the remaining pegasus knight/armour knight and attack that enemy.

If done correctly, the attacking unit will score a critical against that enemy no matter what.