There an npc on the wall on the first floor next to where you first warp in. 1 ash is equivalent to 25 floors. You can go up to 75, from there you have to walk the rest.
I had knowledge of the brazier. I was wondering more on the first 2 sentences of my quote.
If a player is forced to leave the tower, they can re-enter by talking to the stone on the Misty Island again. The exit portal on the 1st floor will warp the player to the floor after the most recent boss floor they have cleared. However, the portal does not correctly warp a player to 26, 51, or 76; the player should use the Immortal Braizer instead to get to those floors.
Taken from the wiki...
From the looks of it, if a player DC's or is forced to respawn, they should: Be able to re-enter ET, and then upon entering the first floor, there should be a warp portal to where you can go through and it will take you the floor after the most recent boss floor that you completed (ie. floors 56, 61, 66, 71). According to the quote from iRO Wiki, you should only need to use the ashes to get floors 26, 51 and 76.