Because 1) draconic grammar is different from English grammar, 2) they can be regularly derived. To get a grasp of what grammatical suffixes are used, it is strongly recommended to read the Lessons. For each suffix separately,

-ing: Draconic does not have continuous aspect "be doing". Instead, use uninflected simple aspect. For verbal adjectives such as "shining sword" there is a special suffix -taas.

-ly: All draconic adjectives can modify verbs, so special adverb suffixes do not exist. "To be eternal" is kos unslaad, while "to live eternally" is lahney unslaad.

-ed: Draconic does not have a simple past inflection. The exceptions are the common verbs los/lost "be/was" and dreh/drey "do/did", which are used before a lexical verb when past tense must be explicit. For verbal adjectives such as "fallen enemy" there is a special suffix -aan.