The new achievements are untranslated so I thought I'd post some rough translations here (using google translate -.-", edited somewhat).
"***june6***archievement[80318]【GW限定】ダンジョンを5個クリアする"
Clear five dungeons * It will be reset at the timing of 0:00 the next day. Please be careful not to forget to receive the reward. Valid until periodic maintenance

"***june6***archievement[80320]【GW限定】「ガーゴイル討伐-呼応-」を25回クリアする"
Assault! Gargoyle Covenant - is cleared 25 times

"***june6***archievement[80321]【GW限定】「ガーゴイル討伐-呼応-」を100回クリアする"
Assault! Gargoyle Covenant - is cleared 100 times

Do you any info about the new ornamentation?
Where to obtain the items

Srayer wrote:Do you any info about the new ornamentation?
Where to obtain the items :?:

The items are:
questItem[4004]【かいかのまがね】大成の勾玉の素材として使用することができます。特定の潜竜の勾玉の解体、または特定のにゃんころポンより入手することが可能です。

questItem[4005]【かいてんのふたば】大成の勾玉の素材として使用することができます。特定の潜竜の勾玉の解体、または特定のにゃんころポンより入手することが可能です

which translate to... no idea. Seems to be related to gacha or something from what I've seen.
My guess is that the mats will become available after the 20th in the Satan Treasure Nyankoropon 2 (Possibly as a side reward for rolling other stuff in the same way as torn gacha tickets).